Incrementing version

Renaming pathtree to expression
Removed global vars
2025-01-18 04:53:17 -08:00 · 2021-01-13 10:29:06 +11:00 · 2021-01-13 10:25:26 +11:00 · 2021-01-13 10:04:52 +11:00 · 2021-01-13 10:00:51 +11:00 · 2021-01-13 09:35:57 +11:00
78 changed files with 1484 additions and 893 deletions
--- a/README.md
+++ b/README.md
@@ -109,6 +109,14 @@ GO111MODULE=on go get github.com/mikefarah/yq
 ## Community Supported Installation methods
 As these are supported by the community :heart: - however, they may be out of date with the officially supported releases.

+# Webi
+
+```
+webi yq
+```
+
+See [webi](https://webinstall.dev/)
+Supported by @adithyasunil26 (https://github.com/webinstall/webi-installers/tree/master/yq)

 ### Windows:
 ```
--- a/cmd/evaluate_all_command.go
+++ b/cmd/evaluate_all_command.go
@@ -59,6 +59,10 @@ func evaluateAll(cmd *cobra.Command, args []string) error {
 		defer func() { writeInPlaceHandler.FinishWriteInPlace(completedSuccessfully) }()
 	}

+	if nullInput && len(args) > 1 {
+		return errors.New("Cannot pass files in when using null-input flag")
+	}
+
 	printer := yqlib.NewPrinter(out, outputToJSON, unwrapScalar, colorsEnabled, indent, !noDocSeparators)

 	allAtOnceEvaluator := yqlib.NewAllAtOnceEvaluator()
--- a/cmd/evalute_sequence_command.go
+++ b/cmd/evalute_sequence_command.go
@@ -83,6 +83,10 @@ func evaluateSequence(cmd *cobra.Command, args []string) error {

 	streamEvaluator := yqlib.NewStreamEvaluator()

+	if nullInput && len(args) > 1 {
+		return errors.New("Cannot pass files in when using null-input flag")
+	}
+
 	switch len(args) {
 	case 0:
 		if pipingStdIn {
--- a/cmd/version.go
+++ b/cmd/version.go
@@ -11,7 +11,7 @@ var (
 	GitDescribe string

 	// Version is main version number that is being run at the moment.
-	Version = "4.2.1"
+	Version = "4.3.2"

 	// VersionPrerelease is a pre-release marker for the version. If this is "" (empty string)
 	// then it means that it is a final release. Otherwise, this is a pre-release
--- a/github-action/Dockerfile
+++ b/github-action/Dockerfile
@@ -1,4 +1,4 @@
-FROM mikefarah/yq:4.2.1
+FROM mikefarah/yq:4.3.2

 COPY entrypoint.sh /entrypoint.sh

--- a/go.mod
+++ b/go.mod
@@ -2,17 +2,15 @@ module github.com/mikefarah/yq/v4

 require (
 	github.com/elliotchance/orderedmap v1.3.0
-	github.com/fatih/color v1.9.0
-	github.com/goccy/go-yaml v1.8.1
-	github.com/jinzhu/copier v0.0.0-20190924061706-b57f9002281a
-	github.com/mattn/go-colorable v0.1.7 // indirect
+	github.com/fatih/color v1.10.0
+	github.com/goccy/go-yaml v1.8.4
+	github.com/jinzhu/copier v0.1.0
 	github.com/spf13/cobra v1.1.1
 	github.com/timtadh/data-structures v0.5.3 // indirect
 	github.com/timtadh/lexmachine v0.2.2
-	golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f // indirect
-	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
+	golang.org/x/sys v0.0.0-20210105210732-16f7687f5001 // indirect
 	gopkg.in/op/go-logging.v1 v1.0.0-20160211212156-b2cb9fa56473
-	gopkg.in/yaml.v3 v3.0.0-20200615113413-eeeca48fe776
+	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b
 )

 go 1.15
--- a/go.sum
+++ b/go.sum
@@ -39,19 +39,21 @@ github.com/dgryski/go-sip13 v0.0.0-20181026042036-e10d5fee7954/go.mod h1:vAd38F8
 github.com/elliotchance/orderedmap v1.3.0 h1:k6m77/d0zCXTjsk12nX40TkEBkSICq8T4s6R6bpCqU0=
 github.com/elliotchance/orderedmap v1.3.0/go.mod h1:8hdSl6jmveQw8ScByd3AaNHNk51RhbTazdqtTty+NFw=
 github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5KwzbycvMj4=
-github.com/fatih/color v1.9.0 h1:8xPHl4/q1VyqGIPif1F+1V3Y3lSmrq01EabUW3CoW5s=
-github.com/fatih/color v1.9.0/go.mod h1:eQcE1qtQxscV5RaZvpXrrb8Drkc3/DdQ+uUYCNjL+zU=
+github.com/fatih/color v1.10.0 h1:s36xzo75JdqLaaWoiEHk767eHiwo0598uUxyfiPkDsg=
+github.com/fatih/color v1.10.0/go.mod h1:ELkj/draVOlAH/xkhN6mQ50Qd0MPOk5AAr3maGEBuJM=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
 github.com/ghodss/yaml v1.0.0/go.mod h1:4dBDuWmgqj2HViK6kFavaiC9ZROes6MMH2rRYeMEF04=
 github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1/go.mod h1:vR7hzQXu2zJy9AVAgeJqvqgH9Q5CA+iKCZ2gyEVpxRU=
 github.com/go-kit/kit v0.8.0/go.mod h1:xBxKIO96dXMWWy0MnWVtmwkA9/13aqxPnvrjFYMA2as=
 github.com/go-logfmt/logfmt v0.3.0/go.mod h1:Qt1PoO58o5twSAckw1HlFXLmHsOX5/0LbT9GBnD5lWE=
 github.com/go-logfmt/logfmt v0.4.0/go.mod h1:3RMwSq7FuexP4Kalkev3ejPJsZTpXXBr9+V4qmtdjCk=
+github.com/go-playground/assert/v2 v2.0.1/go.mod h1:VDjEfimB/XKnb+ZQfWdccd7VUvScMdVu0Titje2rxJ4=
 github.com/go-playground/locales v0.13.0/go.mod h1:taPMhCMXrRLJO55olJkUXHZBHCxTMfnGwq/HNwmWNS8=
 github.com/go-playground/universal-translator v0.17.0/go.mod h1:UkSxE5sNxxRwHyU+Scu5vgOQjsIJAF8j9muTVoKLVtA=
+github.com/go-playground/validator/v10 v10.4.1/go.mod h1:nlOn6nFhuKACm19sB/8EGNn9GlaMV7XkbRSipzJ0Ii4=
 github.com/go-stack/stack v1.8.0/go.mod h1:v0f6uXyyMGvRgIKkXu+yp6POWl0qKG85gN/melR3HDY=
-github.com/goccy/go-yaml v1.8.1 h1:JuZRFlqLM5cWF6A+waL8AKVuCcqvKOuhJtUQI+L3ez0=
-github.com/goccy/go-yaml v1.8.1/go.mod h1:wS4gNoLalDSJxo/SpngzPQ2BN4uuZVLCmbM4S3vd4+Y=
+github.com/goccy/go-yaml v1.8.4 h1:AOEdR7aQgbgwHznGe3BLkDQVujxCPUpHOZZcQcp8Y3M=
+github.com/goccy/go-yaml v1.8.4/go.mod h1:U/jl18uSupI5rdI2jmuCswEA2htH9eXfferR3KfscvA=
 github.com/gogo/protobuf v1.1.1/go.mod h1:r8qH/GZQm5c6nD/R0oafs1akxWv10x8SbQlK7atdtwQ=
 github.com/gogo/protobuf v1.2.1/go.mod h1:hp+jE20tsWTFYpLwKvXlhS1hjn+gTNwPg2I6zVXpSg4=
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
@@ -99,8 +101,8 @@ github.com/hashicorp/memberlist v0.1.3/go.mod h1:ajVTdAv/9Im8oMAAj5G31PhhMCZJV2p
 github.com/hashicorp/serf v0.8.2/go.mod h1:6hOLApaqBFA1NXqRQAsxw9QxuDEvNxSQRwA/JwenrHc=
 github.com/inconshreveable/mousetrap v1.0.0 h1:Z8tu5sraLXCXIcARxBp/8cbvlwVa7Z1NHg9XEKhtSvM=
 github.com/inconshreveable/mousetrap v1.0.0/go.mod h1:PxqpIevigyE2G7u3NXJIT2ANytuPF1OarO4DADm73n8=
-github.com/jinzhu/copier v0.0.0-20190924061706-b57f9002281a h1:zPPuIq2jAWWPTrGt70eK/BSch+gFAGrNzecsoENgu2o=
-github.com/jinzhu/copier v0.0.0-20190924061706-b57f9002281a/go.mod h1:yL958EeXv8Ylng6IfnvG4oflryUi3vgA3xPs9hmII1s=
+github.com/jinzhu/copier v0.1.0 h1:Vh8xALtH3rrKGB/XIRe5d0yCTHPZFauWPLvdpDAbi88=
+github.com/jinzhu/copier v0.1.0/go.mod h1:24xnZezI2Yqac9J61UC6/dG/k76ttpq0DdJI3QmUvro=
 github.com/jonboulle/clockwork v0.1.0/go.mod h1:Ii8DK3G1RaLaWxj9trq07+26W01tbo22gdxWY5EU2bo=
 github.com/json-iterator/go v1.1.6/go.mod h1:+SdeFBvtyEkXs7REEP0seUULqWtbJapLOCVDaaPEHmU=
 github.com/jstemmer/go-junit-report v0.0.0-20190106144839-af01ea7f8024/go.mod h1:6v2b51hI/fHJwM22ozAgKL4VKDeJcHhJFhtBdhmNjmU=
@@ -118,15 +120,9 @@ github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/leodido/go-urn v1.2.0/go.mod h1:+8+nEpDfqqsY+g338gtMEUOtuK+4dEMhiQEgxpxOKII=
 github.com/magiconair/properties v1.8.1/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=
 github.com/mattn/go-colorable v0.0.9/go.mod h1:9vuHe8Xs5qXnSaW/c/ABM9alt+Vo+STaOChaDxuIBZU=
-github.com/mattn/go-colorable v0.1.4 h1:snbPLB8fVfU9iwbbo30TPtbLRzwWu6aJS6Xh4eaaviA=
-github.com/mattn/go-colorable v0.1.4/go.mod h1:U0ppj6V5qS13XJ6of8GYAs25YV2eR4EVcfRqFIhoBtE=
-github.com/mattn/go-colorable v0.1.7 h1:bQGKb3vps/j0E9GfJQ03JyhRuxsvdAanXlT9BTw3mdw=
-github.com/mattn/go-colorable v0.1.7/go.mod h1:u6P/XSegPjTcexA+o6vUJrdnUu04hMope9wVRipJSqc=
+github.com/mattn/go-colorable v0.1.8 h1:c1ghPdyEDarC70ftn0y+A/Ee++9zz8ljHG1b13eJ0s8=
+github.com/mattn/go-colorable v0.1.8/go.mod h1:u6P/XSegPjTcexA+o6vUJrdnUu04hMope9wVRipJSqc=
 github.com/mattn/go-isatty v0.0.3/go.mod h1:M+lRXTBqGeGNdLjl/ufCoiOlB5xdOkqRJdNxMWT7Zi4=
-github.com/mattn/go-isatty v0.0.8/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hdxcsrc5s=
-github.com/mattn/go-isatty v0.0.10/go.mod h1:qgIWMr58cqv1PHHyhnkY9lrL7etaEgOFcMEpPG5Rm84=
-github.com/mattn/go-isatty v0.0.11 h1:FxPOTFNqGkuDUGi3H/qkUbQO4ZiBa2brKq5r0l8TGeM=
-github.com/mattn/go-isatty v0.0.11/go.mod h1:PhnuNfih5lzO57/f3n+odYbM4JtupLOxQOAqxQCu2WE=
 github.com/mattn/go-isatty v0.0.12 h1:wuysRhFDzyxgEmMf5xjvJ2M9dZoWAXNNr5LSBS7uHXY=
 github.com/mattn/go-isatty v0.0.12/go.mod h1:cbi8OIDigv2wuxKPP5vlRcQ1OAZbq2CE4Kysco4FUpU=
 github.com/matttproud/golang_protobuf_extensions v1.0.1/go.mod h1:D8He9yQNgCq6Z5Ld7szi9bcBfOoFv/3dc6xSMkL2PC0=
@@ -204,6 +200,7 @@ golang.org/x/crypto v0.0.0-20181029021203-45a5f77698d3/go.mod h1:6SG95UA2DQfeDnf
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/crypto v0.0.0-20190605123033-f99c8df09eb5/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190306152737-a1d7652674e8/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190510132918-efd6b22b2522/go.mod h1:ZjyILWgesfNpC6sMxTJOJm9Kp84zZh5NQWvqDGG3Qr8=
@@ -251,22 +248,17 @@ golang.org/x/sys v0.0.0-20181026203630-95b1ffbd15a5/go.mod h1:STP8DvDyc/dI5b8T5h
 golang.org/x/sys v0.0.0-20181107165924-66b7b1311ac8/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20181116152217-5ac8a444bdc5/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190312061237-fead79001313/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190502145724-3ef323f4f1fd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190507160741-ecd444e8653b/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190606165138-5da285871e9c/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190624142023-c5567b49c5d0/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20191008105621-543471e840be/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20191010194322-b09406accb47/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20191026070338-33540a1f6037 h1:YyJpGZS1sBuBCzLAR1VEpK193GlqGZbnPFnPV/5Rsb4=
-golang.org/x/sys v0.0.0-20191026070338-33540a1f6037/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200116001909-b77594299b42/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae h1:/WDfKMnPU+m5M4xB+6x4kaepxRw6jWvR5iDRdvjHgy8=
 golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f h1:+Nyd8tzPX9R7BWHguqsrbFdRx3WQ/1ib8I44HXV5yTA=
-golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210105210732-16f7687f5001 h1:/dSxr6gT0FNI1MO5WLJo8mTmItROeOKTkDn+7OwWBos=
+golang.org/x/sys v0.0.0-20210105210732-16f7687f5001/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
@@ -289,10 +281,9 @@ golang.org/x/tools v0.0.0-20190628153133-6cdbf07be9d0/go.mod h1:/rFqwRUd4F7ZHNgw
 golang.org/x/tools v0.0.0-20190816200558-6889da9d5479/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.0.0-20190911174233-4f2ddba30aff/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.0.0-20191012152004-8de300cfc20a/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.0.0-20191112195655-aa38f8e97acc h1:NCy3Ohtk6Iny5V/reW2Ktypo4zIpWBdRJ1uFMjBxdg8=
 golang.org/x/tools v0.0.0-20191112195655-aa38f8e97acc/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898 h1:/atklqdjdhuosWIl6AIbOeHJjicWYPqR9bpxqxYG2pA=
-golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/api v0.4.0/go.mod h1:8k5glujaEP+g9n7WNsDg8QP6cUVNI86fCNMcbazEtwE=
@@ -322,8 +313,6 @@ gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
-gopkg.in/go-playground/assert.v1 v1.2.1/go.mod h1:9RXL0bg/zibRAgZUYszZSwO/z8Y/a8bDuhia5mkpMnE=
-gopkg.in/go-playground/validator.v9 v9.30.0/go.mod h1:+c9/zcJMFNgbLvly1L1V+PpxWdVbfP1avr/N00E2vyQ=
 gopkg.in/ini.v1 v1.51.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
 gopkg.in/op/go-logging.v1 v1.0.0-20160211212156-b2cb9fa56473 h1:6D+BvnJ/j6e222UW8s2qTSe3wGBtvo0MbVQG/c5k8RE=
 gopkg.in/op/go-logging.v1 v1.0.0-20160211212156-b2cb9fa56473/go.mod h1:N1eN2tsCx0Ydtgjl4cqmbRCsY4/+z4cYDeqwZTk6zog=
@@ -335,8 +324,8 @@ gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.8 h1:obN1ZagJSUGI0Ek/LBmuj4SNLPfIny3KsKFopxRdj10=
 gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-gopkg.in/yaml.v3 v3.0.0-20200615113413-eeeca48fe776 h1:tQIYjPdBoyREyB9XMu+nnTclpTYkz2zFM+lzLJFO4gQ=
-gopkg.in/yaml.v3 v3.0.0-20200615113413-eeeca48fe776/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.0-20190106161140-3f1c8253044a/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.0-20190418001031-e561f6794a2a/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
--- a/pkg/yqlib/all_at_once_evaluator.go
+++ b/pkg/yqlib/all_at_once_evaluator.go
@@ -1,29 +1,50 @@
 package yqlib

-import "container/list"
+import (
+	"container/list"

-/**
-	Loads all yaml documents of all files given into memory, then runs the given expression once.
-**/
+	yaml "gopkg.in/yaml.v3"
+)
+
+// A yaml expression evaluator that runs the expression once against all files/nodes in memory.
 type Evaluator interface {
 	EvaluateFiles(expression string, filenames []string, printer Printer) error
+
+	// EvaluateNodes takes an expression and one or more yaml nodes, returning a list of matching candidate nodes
+	EvaluateNodes(expression string, nodes ...*yaml.Node) (*list.List, error)
+
+	// EvaluateCandidateNodes takes an expression and list of candidate nodes, returning a list of matching candidate nodes
+	EvaluateCandidateNodes(expression string, inputCandidateNodes *list.List) (*list.List, error)
 }

 type allAtOnceEvaluator struct {
 	treeNavigator DataTreeNavigator
-	treeCreator   PathTreeCreator
+	treeCreator   ExpressionParser
 }

 func NewAllAtOnceEvaluator() Evaluator {
-	return &allAtOnceEvaluator{treeNavigator: NewDataTreeNavigator(), treeCreator: NewPathTreeCreator()}
+	return &allAtOnceEvaluator{treeNavigator: NewDataTreeNavigator(), treeCreator: NewExpressionParser()}
+}
+
+func (e *allAtOnceEvaluator) EvaluateNodes(expression string, nodes ...*yaml.Node) (*list.List, error) {
+	inputCandidates := list.New()
+	for _, node := range nodes {
+		inputCandidates.PushBack(&CandidateNode{Node: node})
+	}
+	return e.EvaluateCandidateNodes(expression, inputCandidates)
+}
+
+func (e *allAtOnceEvaluator) EvaluateCandidateNodes(expression string, inputCandidates *list.List) (*list.List, error) {
+	node, err := e.treeCreator.ParseExpression(expression)
+	if err != nil {
+		return nil, err
+	}
+	return e.treeNavigator.GetMatchingNodes(inputCandidates, node)
 }

 func (e *allAtOnceEvaluator) EvaluateFiles(expression string, filenames []string, printer Printer) error {
 	fileIndex := 0
-	node, err := treeCreator.ParsePath(expression)
-	if err != nil {
-		return err
-	}
+
 	var allDocuments *list.List = list.New()
 	for _, filename := range filenames {
 		reader, err := readStream(filename)
@@ -37,7 +58,7 @@ func (e *allAtOnceEvaluator) EvaluateFiles(expression string, filenames []string
 		allDocuments.PushBackList(fileDocuments)
 		fileIndex = fileIndex + 1
 	}
-	matches, err := treeNavigator.GetMatchingNodes(allDocuments, node)
+	matches, err := e.EvaluateCandidateNodes(expression, allDocuments)
 	if err != nil {
 		return err
 	}
--- a/pkg/yqlib/all_at_once_evaluator_test.go
+++ b/pkg/yqlib/all_at_once_evaluator_test.go
@@ -0,0 +1,40 @@
+package yqlib
+
+import (
+	"testing"
+
+	"github.com/mikefarah/yq/v4/test"
+)
+
+var evaluateNodesScenario = []expressionScenario{
+	{
+		document:   `a: hello`,
+		expression: `.a`,
+		expected: []string{
+			"D0, P[a], (!!str)::hello\n",
+		},
+	},
+	{
+		document:   `a: hello`,
+		expression: `.`,
+		expected: []string{
+			"D0, P[], (doc)::a: hello\n",
+		},
+	},
+	{
+		document:   `- a: "yes"`,
+		expression: `.[] | has("a")`,
+		expected: []string{
+			"D0, P[0], (!!bool)::true\n",
+		},
+	},
+}
+
+func TestAllAtOnceEvaluateNodes(t *testing.T) {
+	var evaluator = NewAllAtOnceEvaluator()
+	for _, tt := range evaluateNodesScenario {
+		node := test.ParseData(tt.document)
+		list, _ := evaluator.EvaluateNodes(tt.expression, &node)
+		test.AssertResultComplex(t, tt.expected, resultsToString(list))
+	}
+}
--- a/pkg/yqlib/candidate_node.go
+++ b/pkg/yqlib/candidate_node.go
@@ -21,7 +21,23 @@ func (n *CandidateNode) GetKey() string {
 	return fmt.Sprintf("%v - %v", n.Document, n.Path)
 }

-func (n *CandidateNode) CreateChildPath(path interface{}) []interface{} {
+func (n *CandidateNode) CreateChild(path interface{}, node *yaml.Node) *CandidateNode {
+	return &CandidateNode{
+		Node:      node,
+		Path:      n.createChildPath(path),
+		Document:  n.Document,
+		Filename:  n.Filename,
+		FileIndex: n.FileIndex,
+	}
+}
+
+func (n *CandidateNode) createChildPath(path interface{}) []interface{} {
+	if path == nil {
+		newPath := make([]interface{}, len(n.Path))
+		copy(newPath, n.Path)
+		return newPath
+	}
+
 	//don't use append as they may actually modify the path of the orignal node!
 	newPath := make([]interface{}, len(n.Path)+1)
 	copy(newPath, n.Path)
@@ -45,6 +61,7 @@ func (n *CandidateNode) UpdateFrom(other *CandidateNode) {
 	n.Node.Content = other.Node.Content
 	n.Node.Value = other.Node.Value
 	n.Node.Alias = other.Node.Alias
+	n.Node.Anchor = other.Node.Anchor
 }

 func (n *CandidateNode) UpdateAttributesFrom(other *CandidateNode) {
--- a/pkg/yqlib/color_print.go
+++ b/pkg/yqlib/color_print.go
@@ -17,8 +17,8 @@ func format(attr color.Attribute) string {
 	return fmt.Sprintf("%s[%dm", escape, attr)
 }

-func ColorizeAndPrint(bytes []byte, writer io.Writer) error {
-	tokens := lexer.Tokenize(string(bytes))
+func colorizeAndPrint(yamlBytes []byte, writer io.Writer) error {
+	tokens := lexer.Tokenize(string(yamlBytes))
 	var p printer.Printer
 	p.Bool = func() *printer.Property {
 		return &printer.Property{
--- a/pkg/yqlib/data_tree_navigator.go
+++ b/pkg/yqlib/data_tree_navigator.go
@@ -9,10 +9,10 @@ import (
 )

 type DataTreeNavigator interface {
-	// given a list of CandidateEntities and a pathNode,
-	// this will process the list against the given pathNode and return
+	// given a list of CandidateEntities and a expressionNode,
+	// this will process the list against the given expressionNode and return
 	// a new list of matching candidates
-	GetMatchingNodes(matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error)
+	GetMatchingNodes(matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error)
 }

 type dataTreeNavigator struct {
@@ -22,22 +22,22 @@ func NewDataTreeNavigator() DataTreeNavigator {
 	return &dataTreeNavigator{}
 }

-func (d *dataTreeNavigator) GetMatchingNodes(matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
-	if pathNode == nil {
+func (d *dataTreeNavigator) GetMatchingNodes(matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
+	if expressionNode == nil {
 		log.Debugf("getMatchingNodes - nothing to do")
 		return matchingNodes, nil
 	}
-	log.Debugf("Processing Op: %v", pathNode.Operation.toString())
+	log.Debugf("Processing Op: %v", expressionNode.Operation.toString())
 	if log.IsEnabledFor(logging.DEBUG) {
 		for el := matchingNodes.Front(); el != nil; el = el.Next() {
 			log.Debug(NodeToString(el.Value.(*CandidateNode)))
 		}
 	}
 	log.Debug(">>")
-	handler := pathNode.Operation.OperationType.Handler
+	handler := expressionNode.Operation.OperationType.Handler
 	if handler != nil {
-		return handler(d, matchingNodes, pathNode)
+		return handler(d, matchingNodes, expressionNode)
 	}
-	return nil, fmt.Errorf("Unknown operator %v", pathNode.Operation.OperationType)
+	return nil, fmt.Errorf("Unknown operator %v", expressionNode.Operation.OperationType)

 }
--- a/pkg/yqlib/doc/Add.md
+++ b/pkg/yqlib/doc/Add.md
@@ -1,9 +1,9 @@
 Add behaves differently according to the type of the LHS:
 - arrays: concatenate
- number scalars: arithmetic addition (soon)
- string scalars: concatenate (soon)
+- number scalars: arithmetic addition
+- string scalars: concatenate

-Use `+=` as append assign for things like increment. `.a += .x` is equivalent to running `.a |= . + .x`.
+Use `+=` as append assign for things like increment. Note that `.a += .x` is equivalent to running `.a = .a + .x`.

 ## Concatenate and assign arrays
 Given a sample.yml file of:
@@ -67,23 +67,19 @@ will output
 - 2
 ```

-## Add object to array
+## Add new object to array
 Given a sample.yml file of:
 ```yaml
 a:
-  - 1
-  - 2
-c:
-  cat: meow
+  - dog: woof
 ```
 then
 ```bash
-yq eval '.a + .c' sample.yml
+yq eval '.a + {"cat": "meow"}' sample.yml
 ```
 will output
 ```yaml
- 1
- 2
+- dog: woof
 - cat: meow
 ```

@@ -131,3 +127,85 @@ b:
  - 4
 ```

+## String concatenation
+Given a sample.yml file of:
+```yaml
+a: cat
+b: meow
+```
+then
+```bash
+yq eval '.a = .a + .b' sample.yml
+```
+will output
+```yaml
+a: catmeow
+b: meow
+```
+
+## Relative string concatenation
+Given a sample.yml file of:
+```yaml
+a: cat
+b: meow
+```
+then
+```bash
+yq eval '.a += .b' sample.yml
+```
+will output
+```yaml
+a: catmeow
+b: meow
+```
+
+## Number addition - float
+If the lhs or rhs are floats then the expression will be calculated with floats.
+
+Given a sample.yml file of:
+```yaml
+a: 3
+b: 4.9
+```
+then
+```bash
+yq eval '.a = .a + .b' sample.yml
+```
+will output
+```yaml
+a: 7.9
+b: 4.9
+```
+
+## Number addition - int
+If both the lhs and rhs are ints then the expression will be calculated with ints.
+
+Given a sample.yml file of:
+```yaml
+a: 3
+b: 4
+```
+then
+```bash
+yq eval '.a = .a + .b' sample.yml
+```
+will output
+```yaml
+a: 7
+b: 4
+```
+
+## Increment number
+Given a sample.yml file of:
+```yaml
+a: 3
+```
+then
+```bash
+yq eval '.a += 1' sample.yml
+```
+will output
+```yaml
+a: 4
+```
+
--- a/pkg/yqlib/doc/Delete.md
+++ b/pkg/yqlib/doc/Delete.md
@@ -95,3 +95,23 @@ will output
 b: dog
 ```

+## Recursively delete matching keys
+Given a sample.yml file of:
+```yaml
+a:
+  name: frog
+  b:
+    name: blog
+    age: 12
+```
+then
+```bash
+yq eval 'del(.. | select(has("name")).name)' sample.yml
+```
+will output
+```yaml
+a:
+  b:
+    age: 12
+```
+
--- a/pkg/yqlib/doc/Document
+++ b/pkg/yqlib/doc/Document
@@ -1,4 +1,4 @@
-Use the `documentIndex` operator to select nodes of a particular document.
+Use the `documentIndex` operator (or the `di` shorthand) to select nodes of a particular document.
 ## Retrieve a document index
 Given a sample.yml file of:
 ```yaml
--- a/pkg/yqlib/doc/Env
+++ b/pkg/yqlib/doc/Env
@@ -0,0 +1,78 @@
+This operator is used to handle environment variables usage in path expressions. While environment variables can, of course, be passed in via your CLI with string interpolation, this often comes with complex quote escaping and can be tricky to write and read. Note that there are two forms, `env` which will parse the environment variable as a yaml (be it a map, array, string, number of boolean) and `strenv` which will always parse the argument as a string.
+
+
+## Read string environment variable
+Running
+```bash
+myenv="cat meow" yq eval --null-input '.a = env(myenv)'
+```
+will output
+```yaml
+a: cat meow
+```
+
+## Read boolean environment variable
+Running
+```bash
+myenv="true" yq eval --null-input '.a = env(myenv)'
+```
+will output
+```yaml
+a: true
+```
+
+## Read numeric environment variable
+Running
+```bash
+myenv="12" yq eval --null-input '.a = env(myenv)'
+```
+will output
+```yaml
+a: 12
+```
+
+## Read yaml environment variable
+Running
+```bash
+myenv="{b: fish}" yq eval --null-input '.a = env(myenv)'
+```
+will output
+```yaml
+a: {b: fish}
+```
+
+## Read boolean environment variable as a string
+Running
+```bash
+myenv="true" yq eval --null-input '.a = strenv(myenv)'
+```
+will output
+```yaml
+a: "true"
+```
+
+## Read numeric environment variable as a string
+Running
+```bash
+myenv="12" yq eval --null-input '.a = strenv(myenv)'
+```
+will output
+```yaml
+a: "12"
+```
+
+## Dynamic key lookup with environment variable
+Given a sample.yml file of:
+```yaml
+cat: meow
+dog: woof
+```
+then
+```bash
+myenv="cat" yq eval '.[env(myenv)]' sample.yml
+```
+will output
+```yaml
+meow
+```
+
--- a/pkg/yqlib/doc/Multiply.md
+++ b/pkg/yqlib/doc/Multiply.md
@@ -180,7 +180,7 @@ g: thongs
 f: *cat
 ```

-## Merge does not copy anchor names
+## Merge copies anchor names
 Given a sample.yml file of:
 ```yaml
 a:
@@ -197,7 +197,7 @@ yq eval '.c * .a' sample.yml
 will output
 ```yaml
 g: thongs
-c: frog
+c: &cat frog
 ```

 ## Merge with merge anchors
--- a/pkg/yqlib/doc/Recursive
+++ b/pkg/yqlib/doc/Recursive
@@ -1,4 +1,4 @@
-This operator recursively matches all children nodes given of a particular element, including that node itself. This is most often used to apply a filter recursively against all matches. It can be used in either the 
+This operator recursively matches (or globs) all children nodes given of a particular element, including that node itself. This is most often used to apply a filter recursively against all matches. It can be used in either the 

 ## match values form `..`
 This will, like the `jq` equivalent, recursively match all _value_ nodes. Use it to find/manipulate particular values.
@@ -32,6 +32,50 @@ a: frog
 frog
 ```

+## Recursively find nodes with keys
+Note that this example has wrapped the expression in `[]` to show that there are two matches returned. You do not have to wrap in `[]` in your path expression.
+
+Given a sample.yml file of:
+```yaml
+a:
+  name: frog
+  b:
+    name: blog
+    age: 12
+```
+then
+```bash
+yq eval '[.. | select(has("name"))]' sample.yml
+```
+will output
+```yaml
+- name: frog
+  b:
+    name: blog
+    age: 12
+- name: blog
+  age: 12
+```
+
+## Recursively find nodes with values
+Given a sample.yml file of:
+```yaml
+a:
+  nameA: frog
+  b:
+    nameB: frog
+    age: 12
+```
+then
+```bash
+yq eval '.. | select(. == "frog")' sample.yml
+```
+will output
+```yaml
+frog
+frog
+```
+
 ## Recurse map (values and keys)
 Note that the map key appears in the results

--- a/pkg/yqlib/doc/Traverse.md
+++ b/pkg/yqlib/doc/Traverse.md
@@ -48,6 +48,24 @@ will output
 frog
 ```

+## Dynamic keys
+Expressions within [] can be used to dynamically lookup / calculate keys
+
+Given a sample.yml file of:
+```yaml
+b: apple
+apple: crispy yum
+banana: soft yum
+```
+then
+```bash
+yq eval '.[.b]' sample.yml
+```
+will output
+```yaml
+crispy yum
+```
+
 ## Children don't exist
 Nodes are added dynamically while traversing

--- a/pkg/yqlib/doc/headers/Add.md
+++ b/pkg/yqlib/doc/headers/Add.md
@@ -1,6 +1,6 @@
 Add behaves differently according to the type of the LHS:
 - arrays: concatenate
- number scalars: arithmetic addition (soon)
- string scalars: concatenate (soon)
+- number scalars: arithmetic addition
+- string scalars: concatenate

-Use `+=` as append assign for things like increment. `.a += .x` is equivalent to running `.a |= . + .x`.
+Use `+=` as append assign for things like increment. Note that `.a += .x` is equivalent to running `.a = .a + .x`.
--- a/pkg/yqlib/doc/headers/Document
+++ b/pkg/yqlib/doc/headers/Document
@@ -1 +1 @@
-Use the `documentIndex` operator to select nodes of a particular document.
+Use the `documentIndex` operator (or the `di` shorthand) to select nodes of a particular document.
--- a/pkg/yqlib/doc/headers/Env
+++ b/pkg/yqlib/doc/headers/Env
@@ -0,0 +1,2 @@
+This operator is used to handle environment variables usage in path expressions. While environment variables can, of course, be passed in via your CLI with string interpolation, this often comes with complex quote escaping and can be tricky to write and read. Note that there are two forms, `env` which will parse the environment variable as a yaml (be it a map, array, string, number of boolean) and `strenv` which will always parse the argument as a string.
+
--- a/pkg/yqlib/doc/headers/Recursive
+++ b/pkg/yqlib/doc/headers/Recursive
@@ -1,4 +1,4 @@
-This operator recursively matches all children nodes given of a particular element, including that node itself. This is most often used to apply a filter recursively against all matches. It can be used in either the 
+This operator recursively matches (or globs) all children nodes given of a particular element, including that node itself. This is most often used to apply a filter recursively against all matches. It can be used in either the 

 ## match values form `..`
 This will, like the `jq` equivalent, recursively match all _value_ nodes. Use it to find/manipulate particular values.
--- a/pkg/yqlib/encoder.go
+++ b/pkg/yqlib/encoder.go
@@ -50,7 +50,7 @@ func (ye *yamlEncoder) Encode(node *yaml.Node) error {
 	}

 	if ye.colorise {
-		return ColorizeAndPrint(tempBuffer.Bytes(), ye.destination)
+		return colorizeAndPrint(tempBuffer.Bytes(), ye.destination)
 	}
 	return nil
 }
--- a/pkg/yqlib/expression_parser.go
+++ b/pkg/yqlib/expression_parser.go
@@ -5,29 +5,28 @@ import (
 	"strings"
 )

-var myPathTokeniser = NewPathTokeniser()
-var myPathPostfixer = NewPathPostFixer()
+var myPathTokeniser = newExpressionTokeniser()
+var myPathPostfixer = newExpressionPostFixer()

-type PathTreeNode struct {
+type ExpressionNode struct {
 	Operation *Operation
-	Lhs       *PathTreeNode
-	Rhs       *PathTreeNode
+	Lhs       *ExpressionNode
+	Rhs       *ExpressionNode
 }

-type PathTreeCreator interface {
-	ParsePath(path string) (*PathTreeNode, error)
-	CreatePathTree(postFixPath []*Operation) (*PathTreeNode, error)
+type ExpressionParser interface {
+	ParseExpression(expression string) (*ExpressionNode, error)
 }

-type pathTreeCreator struct {
+type expressionParserImpl struct {
 }

-func NewPathTreeCreator() PathTreeCreator {
-	return &pathTreeCreator{}
+func NewExpressionParser() ExpressionParser {
+	return &expressionParserImpl{}
 }

-func (p *pathTreeCreator) ParsePath(path string) (*PathTreeNode, error) {
-	tokens, err := myPathTokeniser.Tokenise(path)
+func (p *expressionParserImpl) ParseExpression(expression string) (*ExpressionNode, error) {
+	tokens, err := myPathTokeniser.Tokenise(expression)
 	if err != nil {
 		return nil, err
 	}
@@ -36,18 +35,18 @@ func (p *pathTreeCreator) ParsePath(path string) (*PathTreeNode, error) {
 	if err != nil {
 		return nil, err
 	}
-	return p.CreatePathTree(Operations)
+	return p.createExpressionTree(Operations)
 }

-func (p *pathTreeCreator) CreatePathTree(postFixPath []*Operation) (*PathTreeNode, error) {
-	var stack = make([]*PathTreeNode, 0)
+func (p *expressionParserImpl) createExpressionTree(postFixPath []*Operation) (*ExpressionNode, error) {
+	var stack = make([]*ExpressionNode, 0)

 	if len(postFixPath) == 0 {
 		return nil, nil
 	}

 	for _, Operation := range postFixPath {
-		var newNode = PathTreeNode{Operation: Operation}
+		var newNode = ExpressionNode{Operation: Operation}
 		log.Debugf("pathTree %v ", Operation.toString())
 		if Operation.OperationType.NumArgs > 0 {
 			numArgs := Operation.OperationType.NumArgs
--- a/pkg/yqlib/expression_parser_test.go
+++ b/pkg/yqlib/expression_parser_test.go
@@ -7,36 +7,36 @@ import (
 )

 func TestPathTreeNoArgsForTwoArgOp(t *testing.T) {
-	_, err := treeCreator.ParsePath("=")
+	_, err := NewExpressionParser().ParseExpression("=")
 	test.AssertResultComplex(t, "'=' expects 2 args but there is 0", err.Error())
 }

 func TestPathTreeOneLhsArgsForTwoArgOp(t *testing.T) {
-	_, err := treeCreator.ParsePath(".a =")
+	_, err := NewExpressionParser().ParseExpression(".a =")
 	test.AssertResultComplex(t, "'=' expects 2 args but there is 1", err.Error())
 }

 func TestPathTreeOneRhsArgsForTwoArgOp(t *testing.T) {
-	_, err := treeCreator.ParsePath("= .a")
+	_, err := NewExpressionParser().ParseExpression("= .a")
 	test.AssertResultComplex(t, "'=' expects 2 args but there is 1", err.Error())
 }

 func TestPathTreeTwoArgsForTwoArgOp(t *testing.T) {
-	_, err := treeCreator.ParsePath(".a = .b")
+	_, err := NewExpressionParser().ParseExpression(".a = .b")
 	test.AssertResultComplex(t, nil, err)
 }

 func TestPathTreeNoArgsForOneArgOp(t *testing.T) {
-	_, err := treeCreator.ParsePath("explode")
+	_, err := NewExpressionParser().ParseExpression("explode")
 	test.AssertResultComplex(t, "'explode' expects 1 arg but received none", err.Error())
 }

 func TestPathTreeOneArgForOneArgOp(t *testing.T) {
-	_, err := treeCreator.ParsePath("explode(.)")
+	_, err := NewExpressionParser().ParseExpression("explode(.)")
 	test.AssertResultComplex(t, nil, err)
 }

 func TestPathTreeExtraArgs(t *testing.T) {
-	_, err := treeCreator.ParsePath("sortKeys(.) explode(.)")
+	_, err := NewExpressionParser().ParseExpression("sortKeys(.) explode(.)")
 	test.AssertResultComplex(t, "expected end of expression but found 'explode', please check expression syntax", err.Error())
 }
--- a/pkg/yqlib/expression_postfix.go
+++ b/pkg/yqlib/expression_postfix.go
@@ -6,40 +6,40 @@ import (
 	logging "gopkg.in/op/go-logging.v1"
 )

-type PathPostFixer interface {
-	ConvertToPostfix([]*Token) ([]*Operation, error)
+type expressionPostFixer interface {
+	ConvertToPostfix([]*token) ([]*Operation, error)
 }

-type pathPostFixer struct {
+type expressionPostFixerImpl struct {
 }

-func NewPathPostFixer() PathPostFixer {
-	return &pathPostFixer{}
+func newExpressionPostFixer() expressionPostFixer {
+	return &expressionPostFixerImpl{}
 }

-func popOpToResult(opStack []*Token, result []*Operation) ([]*Token, []*Operation) {
-	var newOp *Token
+func popOpToResult(opStack []*token, result []*Operation) ([]*token, []*Operation) {
+	var newOp *token
 	opStack, newOp = opStack[0:len(opStack)-1], opStack[len(opStack)-1]
 	return opStack, append(result, newOp.Operation)
 }

-func (p *pathPostFixer) ConvertToPostfix(infixTokens []*Token) ([]*Operation, error) {
+func (p *expressionPostFixerImpl) ConvertToPostfix(infixTokens []*token) ([]*Operation, error) {
 	var result []*Operation
 	// surround the whole thing with quotes
-	var opStack = []*Token{&Token{TokenType: OpenBracket}}
-	var tokens = append(infixTokens, &Token{TokenType: CloseBracket})
+	var opStack = []*token{&token{TokenType: openBracket}}
+	var tokens = append(infixTokens, &token{TokenType: closeBracket})

-	for _, token := range tokens {
-		log.Debugf("postfix processing token %v, %v", token.toString(), token.Operation)
-		switch token.TokenType {
-		case OpenBracket, OpenCollect, OpenCollectObject:
-			opStack = append(opStack, token)
-		case CloseCollect, CloseCollectObject:
-			var opener TokenType = OpenCollect
-			var collectOperator *OperationType = Collect
-			if token.TokenType == CloseCollectObject {
-				opener = OpenCollectObject
-				collectOperator = CollectObject
+	for _, currentToken := range tokens {
+		log.Debugf("postfix processing currentToken %v, %v", currentToken.toString(), currentToken.Operation)
+		switch currentToken.TokenType {
+		case openBracket, openCollect, openCollectObject:
+			opStack = append(opStack, currentToken)
+		case closeCollect, closeCollectObject:
+			var opener tokenType = openCollect
+			var collectOperator *operationType = collectOpType
+			if currentToken.TokenType == closeCollectObject {
+				opener = openCollectObject
+				collectOperator = collectObjectOpType
 			}
 			itemsInMiddle := false
 			for len(opStack) > 0 && opStack[len(opStack)-1].TokenType != opener {
@@ -48,7 +48,7 @@ func (p *pathPostFixer) ConvertToPostfix(infixTokens []*Token) ([]*Operation, er
 			}
 			if !itemsInMiddle {
 				// must be an empty collection, add the empty object as a LHS parameter
-				result = append(result, &Operation{OperationType: Empty})
+				result = append(result, &Operation{OperationType: emptyOpType})
 			}
 			if len(opStack) == 0 {
 				return nil, errors.New("Bad path expression, got close collect brackets without matching opening bracket")
@@ -56,10 +56,10 @@ func (p *pathPostFixer) ConvertToPostfix(infixTokens []*Token) ([]*Operation, er
 			// now we should have [] as the last element on the opStack, get rid of it
 			opStack = opStack[0 : len(opStack)-1]
 			//and append a collect to the opStack
-			opStack = append(opStack, &Token{TokenType: OperationToken, Operation: &Operation{OperationType: ShortPipe}})
-			opStack = append(opStack, &Token{TokenType: OperationToken, Operation: &Operation{OperationType: collectOperator}})
-		case CloseBracket:
-			for len(opStack) > 0 && opStack[len(opStack)-1].TokenType != OpenBracket {
+			opStack = append(opStack, &token{TokenType: operationToken, Operation: &Operation{OperationType: shortPipeOpType}})
+			opStack = append(opStack, &token{TokenType: operationToken, Operation: &Operation{OperationType: collectOperator}})
+		case closeBracket:
+			for len(opStack) > 0 && opStack[len(opStack)-1].TokenType != openBracket {
 				opStack, result = popOpToResult(opStack, result)
 			}
 			if len(opStack) == 0 {
@@ -69,22 +69,22 @@ func (p *pathPostFixer) ConvertToPostfix(infixTokens []*Token) ([]*Operation, er
 			opStack = opStack[0 : len(opStack)-1]

 		default:
-			var currentPrecedence = token.Operation.OperationType.Precedence
+			var currentPrecedence = currentToken.Operation.OperationType.Precedence
 			// pop off higher precedent operators onto the result
 			for len(opStack) > 0 &&
-				opStack[len(opStack)-1].TokenType == OperationToken &&
+				opStack[len(opStack)-1].TokenType == operationToken &&
 				opStack[len(opStack)-1].Operation.OperationType.Precedence >= currentPrecedence {
 				opStack, result = popOpToResult(opStack, result)
 			}
 			// add this operator to the opStack
-			opStack = append(opStack, token)
+			opStack = append(opStack, currentToken)
 		}
 	}

 	if log.IsEnabledFor(logging.DEBUG) {
 		log.Debugf("PostFix Result:")
-		for _, token := range result {
-			log.Debugf("> %v", token.toString())
+		for _, currentToken := range result {
+			log.Debugf("> %v", currentToken.toString())
 		}
 	}

--- a/pkg/yqlib/expression_processing_test.go
+++ b/pkg/yqlib/expression_processing_test.go
@@ -164,8 +164,8 @@ var pathTests = []struct {
 	},
 }

-var tokeniser = NewPathTokeniser()
-var postFixer = NewPathPostFixer()
+var tokeniser = newExpressionTokeniser()
+var postFixer = newExpressionPostFixer()

 func TestPathParsing(t *testing.T) {
 	for _, tt := range pathTests {
--- a/pkg/yqlib/expression_tokeniser.go
+++ b/pkg/yqlib/expression_tokeniser.go
@@ -0,0 +1,407 @@
+package yqlib
+
+import (
+	"fmt"
+	"strconv"
+
+	lex "github.com/timtadh/lexmachine"
+	"github.com/timtadh/lexmachine/machines"
+)
+
+func skip(*lex.Scanner, *machines.Match) (interface{}, error) {
+	return nil, nil
+}
+
+type tokenType uint32
+
+const (
+	operationToken = 1 << iota
+	openBracket
+	closeBracket
+	openCollect
+	closeCollect
+	openCollectObject
+	closeCollectObject
+	traverseArrayCollect
+)
+
+type token struct {
+	TokenType            tokenType
+	Operation            *Operation
+	AssignOperation      *Operation // e.g. tag (GetTag) op becomes AssignTag if '=' follows it
+	CheckForPostTraverse bool       // e.g. [1]cat should really be [1].cat
+
+}
+
+func (t *token) toString() string {
+	if t.TokenType == operationToken {
+		log.Debug("toString, its an op")
+		return t.Operation.toString()
+	} else if t.TokenType == openBracket {
+		return "("
+	} else if t.TokenType == closeBracket {
+		return ")"
+	} else if t.TokenType == openCollect {
+		return "["
+	} else if t.TokenType == closeCollect {
+		return "]"
+	} else if t.TokenType == openCollectObject {
+		return "{"
+	} else if t.TokenType == closeCollectObject {
+		return "}"
+	} else if t.TokenType == traverseArrayCollect {
+		return ".["
+
+	} else {
+		return "NFI"
+	}
+}
+
+func pathToken(wrapped bool) lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		value := string(m.Bytes)
+		value = value[1:]
+		if wrapped {
+			value = unwrap(value)
+		}
+		log.Debug("PathToken %v", value)
+		op := &Operation{OperationType: traversePathOpType, Value: value, StringValue: value}
+		return &token{TokenType: operationToken, Operation: op, CheckForPostTraverse: true}, nil
+	}
+}
+
+func documentToken() lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		var numberString = string(m.Bytes)
+		numberString = numberString[1:]
+		var number, errParsingInt = strconv.ParseInt(numberString, 10, 64) // nolint
+		if errParsingInt != nil {
+			return nil, errParsingInt
+		}
+		log.Debug("documentToken %v", string(m.Bytes))
+		op := &Operation{OperationType: documentFilterOpType, Value: number, StringValue: numberString}
+		return &token{TokenType: operationToken, Operation: op, CheckForPostTraverse: true}, nil
+	}
+}
+
+func opToken(op *operationType) lex.Action {
+	return opTokenWithPrefs(op, nil, nil)
+}
+
+func opAssignableToken(opType *operationType, assignOpType *operationType) lex.Action {
+	return opTokenWithPrefs(opType, assignOpType, nil)
+}
+
+func assignOpToken(updateAssign bool) lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		log.Debug("assignOpToken %v", string(m.Bytes))
+		value := string(m.Bytes)
+		op := &Operation{OperationType: assignOpType, Value: assignOpType.Type, StringValue: value, UpdateAssign: updateAssign}
+		return &token{TokenType: operationToken, Operation: op}, nil
+	}
+}
+
+func opTokenWithPrefs(op *operationType, assignOpType *operationType, preferences interface{}) lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		log.Debug("opTokenWithPrefs %v", string(m.Bytes))
+		value := string(m.Bytes)
+		op := &Operation{OperationType: op, Value: op.Type, StringValue: value, Preferences: preferences}
+		var assign *Operation
+		if assignOpType != nil {
+			assign = &Operation{OperationType: assignOpType, Value: assignOpType.Type, StringValue: value, Preferences: preferences}
+		}
+		return &token{TokenType: operationToken, Operation: op, AssignOperation: assign}, nil
+	}
+}
+
+func assignAllCommentsOp(updateAssign bool) lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		log.Debug("assignAllCommentsOp %v", string(m.Bytes))
+		value := string(m.Bytes)
+		op := &Operation{
+			OperationType: assignCommentOpType,
+			Value:         assignCommentOpType.Type,
+			StringValue:   value,
+			UpdateAssign:  updateAssign,
+			Preferences:   &commentOpPreferences{LineComment: true, HeadComment: true, FootComment: true},
+		}
+		return &token{TokenType: operationToken, Operation: op}, nil
+	}
+}
+
+func literalToken(pType tokenType, checkForPost bool) lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		return &token{TokenType: pType, CheckForPostTraverse: checkForPost}, nil
+	}
+}
+
+func unwrap(value string) string {
+	return value[1 : len(value)-1]
+}
+
+func numberValue() lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		var numberString = string(m.Bytes)
+		var number, errParsingInt = strconv.ParseInt(numberString, 10, 64) // nolint
+		if errParsingInt != nil {
+			return nil, errParsingInt
+		}
+
+		return &token{TokenType: operationToken, Operation: createValueOperation(number, numberString)}, nil
+	}
+}
+
+func floatValue() lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		var numberString = string(m.Bytes)
+		var number, errParsingInt = strconv.ParseFloat(numberString, 64) // nolint
+		if errParsingInt != nil {
+			return nil, errParsingInt
+		}
+		return &token{TokenType: operationToken, Operation: createValueOperation(number, numberString)}, nil
+	}
+}
+
+func booleanValue(val bool) lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		return &token{TokenType: operationToken, Operation: createValueOperation(val, string(m.Bytes))}, nil
+	}
+}
+
+func stringValue(wrapped bool) lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		value := string(m.Bytes)
+		if wrapped {
+			value = unwrap(value)
+		}
+		return &token{TokenType: operationToken, Operation: createValueOperation(value, value)}, nil
+	}
+}
+
+func envOp(strenv bool) lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		value := string(m.Bytes)
+		preferences := &envOpPreferences{}
+
+		if strenv {
+			// strenv( )
+			value = value[7 : len(value)-1]
+			preferences.StringValue = true
+		} else {
+			//env( )
+			value = value[4 : len(value)-1]
+		}
+
+		envOperation := createValueOperation(value, value)
+		envOperation.OperationType = envOpType
+		envOperation.Preferences = preferences
+
+		return &token{TokenType: operationToken, Operation: envOperation}, nil
+	}
+}
+
+func nullValue() lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		return &token{TokenType: operationToken, Operation: createValueOperation(nil, string(m.Bytes))}, nil
+	}
+}
+
+func selfToken() lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		op := &Operation{OperationType: selfReferenceOpType}
+		return &token{TokenType: operationToken, Operation: op}, nil
+	}
+}
+
+func initLexer() (*lex.Lexer, error) {
+	lexer := lex.NewLexer()
+	lexer.Add([]byte(`\(`), literalToken(openBracket, false))
+	lexer.Add([]byte(`\)`), literalToken(closeBracket, true))
+
+	lexer.Add([]byte(`\.\[`), literalToken(traverseArrayCollect, false))
+	lexer.Add([]byte(`\.\.`), opTokenWithPrefs(recursiveDescentOpType, nil, &recursiveDescentPreferences{RecurseArray: true,
+		TraversePreferences: &traversePreferences{FollowAlias: false, IncludeMapKeys: false}}))
+
+	lexer.Add([]byte(`\.\.\.`), opTokenWithPrefs(recursiveDescentOpType, nil, &recursiveDescentPreferences{RecurseArray: true,
+		TraversePreferences: &traversePreferences{FollowAlias: false, IncludeMapKeys: true}}))
+
+	lexer.Add([]byte(`,`), opToken(unionOpType))
+	lexer.Add([]byte(`:\s*`), opToken(createMapOpType))
+	lexer.Add([]byte(`length`), opToken(lengthOpType))
+	lexer.Add([]byte(`sortKeys`), opToken(sortKeysOpType))
+	lexer.Add([]byte(`select`), opToken(selectOpType))
+	lexer.Add([]byte(`has`), opToken(hasOpType))
+	lexer.Add([]byte(`explode`), opToken(explodeOpType))
+	lexer.Add([]byte(`or`), opToken(orOpType))
+	lexer.Add([]byte(`and`), opToken(andOpType))
+	lexer.Add([]byte(`not`), opToken(notOpType))
+	lexer.Add([]byte(`\/\/`), opToken(alternativeOpType))
+
+	lexer.Add([]byte(`documentIndex`), opToken(getDocumentIndexOpType))
+	lexer.Add([]byte(`di`), opToken(getDocumentIndexOpType))
+
+	lexer.Add([]byte(`style`), opAssignableToken(getStyleOpType, assignStyleOpType))
+
+	lexer.Add([]byte(`tag`), opAssignableToken(getTagOpType, assignTagOpType))
+	lexer.Add([]byte(`anchor`), opAssignableToken(getAnchorOpType, assignAnchorOpType))
+	lexer.Add([]byte(`alias`), opAssignableToken(getAliasOptype, assignAliasOpType))
+	lexer.Add([]byte(`filename`), opToken(getFilenameOpType))
+	lexer.Add([]byte(`fileIndex`), opToken(getFileIndexOpType))
+	lexer.Add([]byte(`fi`), opToken(getFileIndexOpType))
+	lexer.Add([]byte(`path`), opToken(getPathOpType))
+
+	lexer.Add([]byte(`lineComment`), opTokenWithPrefs(getCommentOpType, assignCommentOpType, &commentOpPreferences{LineComment: true}))
+
+	lexer.Add([]byte(`headComment`), opTokenWithPrefs(getCommentOpType, assignCommentOpType, &commentOpPreferences{HeadComment: true}))
+
+	lexer.Add([]byte(`footComment`), opTokenWithPrefs(getCommentOpType, assignCommentOpType, &commentOpPreferences{FootComment: true}))
+
+	lexer.Add([]byte(`comments\s*=`), assignAllCommentsOp(false))
+	lexer.Add([]byte(`comments\s*\|=`), assignAllCommentsOp(true))
+
+	lexer.Add([]byte(`collect`), opToken(collectOpType))
+
+	lexer.Add([]byte(`\s*==\s*`), opToken(equalsOpType))
+	lexer.Add([]byte(`\s*=\s*`), assignOpToken(false))
+
+	lexer.Add([]byte(`del`), opToken(deleteChildOpType))
+
+	lexer.Add([]byte(`\s*\|=\s*`), assignOpToken(true))
+
+	lexer.Add([]byte("( |\t|\n|\r)+"), skip)
+
+	lexer.Add([]byte(`d[0-9]+`), documentToken())
+	lexer.Add([]byte(`\."[^ "]+"`), pathToken(true))
+	lexer.Add([]byte(`\.[^ \}\{\:\[\],\|\.\[\(\)=]+`), pathToken(false))
+	lexer.Add([]byte(`\.`), selfToken())
+
+	lexer.Add([]byte(`\|`), opToken(pipeOpType))
+
+	lexer.Add([]byte(`-?\d+(\.\d+)`), floatValue())
+	lexer.Add([]byte(`-?[1-9](\.\d+)?[Ee][-+]?\d+`), floatValue())
+	lexer.Add([]byte(`-?\d+`), numberValue())
+
+	lexer.Add([]byte(`[Tt][Rr][Uu][Ee]`), booleanValue(true))
+	lexer.Add([]byte(`[Ff][Aa][Ll][Ss][Ee]`), booleanValue(false))
+
+	lexer.Add([]byte(`[Nn][Uu][Ll][Ll]`), nullValue())
+	lexer.Add([]byte(`~`), nullValue())
+
+	lexer.Add([]byte(`"[^"]*"`), stringValue(true))
+	lexer.Add([]byte(`strenv\([^\)]+\)`), envOp(true))
+	lexer.Add([]byte(`env\([^\)]+\)`), envOp(false))
+
+	lexer.Add([]byte(`\[`), literalToken(openCollect, false))
+	lexer.Add([]byte(`\]`), literalToken(closeCollect, true))
+	lexer.Add([]byte(`\{`), literalToken(openCollectObject, false))
+	lexer.Add([]byte(`\}`), literalToken(closeCollectObject, true))
+	lexer.Add([]byte(`\*`), opTokenWithPrefs(multiplyOpType, nil, &multiplyPreferences{AppendArrays: false}))
+	lexer.Add([]byte(`\*\+`), opTokenWithPrefs(multiplyOpType, nil, &multiplyPreferences{AppendArrays: true}))
+	lexer.Add([]byte(`\+`), opToken(addOpType))
+	lexer.Add([]byte(`\+=`), opToken(addAssignOpType))
+
+	err := lexer.Compile()
+	if err != nil {
+		return nil, err
+	}
+	return lexer, nil
+}
+
+type expressionTokeniser interface {
+	Tokenise(expression string) ([]*token, error)
+}
+
+type expressionTokeniserImpl struct {
+	lexer *lex.Lexer
+}
+
+func newExpressionTokeniser() expressionTokeniser {
+	var lexer, err = initLexer()
+	if err != nil {
+		panic(err)
+	}
+	return &expressionTokeniserImpl{lexer}
+}
+
+func (p *expressionTokeniserImpl) Tokenise(expression string) ([]*token, error) {
+	scanner, err := p.lexer.Scanner([]byte(expression))
+
+	if err != nil {
+		return nil, fmt.Errorf("Parsing expression: %v", err)
+	}
+	var tokens []*token
+	for tok, err, eof := scanner.Next(); !eof; tok, err, eof = scanner.Next() {
+
+		if tok != nil {
+			currentToken := tok.(*token)
+			log.Debugf("Tokenising %v", currentToken.toString())
+			tokens = append(tokens, currentToken)
+		}
+		if err != nil {
+			return nil, fmt.Errorf("Parsing expression: %v", err)
+		}
+	}
+	var postProcessedTokens = make([]*token, 0)
+
+	skipNextToken := false
+
+	for index := range tokens {
+		if skipNextToken {
+			skipNextToken = false
+		} else {
+			postProcessedTokens, skipNextToken = p.handleToken(tokens, index, postProcessedTokens)
+		}
+	}
+
+	return postProcessedTokens, nil
+}
+
+func (p *expressionTokeniserImpl) handleToken(tokens []*token, index int, postProcessedTokens []*token) (tokensAccum []*token, skipNextToken bool) {
+	skipNextToken = false
+	currentToken := tokens[index]
+
+	if currentToken.TokenType == traverseArrayCollect {
+		//need to put a traverse array then a collect currentToken
+		// do this by adding traverse then converting currentToken to collect
+
+		op := &Operation{OperationType: traverseArrayOpType, StringValue: "TRAVERSE_ARRAY"}
+		postProcessedTokens = append(postProcessedTokens, &token{TokenType: operationToken, Operation: op})
+
+		currentToken = &token{TokenType: openCollect}
+
+	}
+
+	if index != len(tokens)-1 && currentToken.AssignOperation != nil &&
+		tokens[index+1].TokenType == operationToken &&
+		tokens[index+1].Operation.OperationType == assignOpType {
+		currentToken.Operation = currentToken.AssignOperation
+		currentToken.Operation.UpdateAssign = tokens[index+1].Operation.UpdateAssign
+		skipNextToken = true
+	}
+
+	postProcessedTokens = append(postProcessedTokens, currentToken)
+
+	if index != len(tokens)-1 && currentToken.CheckForPostTraverse &&
+		tokens[index+1].TokenType == operationToken &&
+		tokens[index+1].Operation.OperationType == traversePathOpType {
+		op := &Operation{OperationType: shortPipeOpType, Value: "PIPE"}
+		postProcessedTokens = append(postProcessedTokens, &token{TokenType: operationToken, Operation: op})
+	}
+	if index != len(tokens)-1 && currentToken.CheckForPostTraverse &&
+		tokens[index+1].TokenType == openCollect {
+
+		op := &Operation{OperationType: shortPipeOpType, Value: "PIPE"}
+		postProcessedTokens = append(postProcessedTokens, &token{TokenType: operationToken, Operation: op})
+
+		op = &Operation{OperationType: traverseArrayOpType}
+		postProcessedTokens = append(postProcessedTokens, &token{TokenType: operationToken, Operation: op})
+	}
+	if index != len(tokens)-1 && currentToken.CheckForPostTraverse &&
+		tokens[index+1].TokenType == traverseArrayCollect {
+
+		op := &Operation{OperationType: shortPipeOpType, Value: "PIPE"}
+		postProcessedTokens = append(postProcessedTokens, &token{TokenType: operationToken, Operation: op})
+
+	}
+	return postProcessedTokens, skipNextToken
+}
--- a/pkg/yqlib/lib.go
+++ b/pkg/yqlib/lib.go
@@ -1,3 +1,5 @@
+// Use the top level Evaluator or StreamEvaluator to evaluate expressions and return matches.
+//
 package yqlib

 import (
@@ -11,85 +13,85 @@ import (

 var log = logging.MustGetLogger("yq-lib")

-type OperationType struct {
+type operationType struct {
 	Type       string
 	NumArgs    uint // number of arguments to the op
 	Precedence uint
-	Handler    OperatorHandler
+	Handler    operatorHandler
 }

 // operators TODO:
-// - keys operator for controlling key metadata (particularly anchors/aliases)
 // - mergeEmpty (sets only if the document is empty, do I do that now?)

-var Or = &OperationType{Type: "OR", NumArgs: 2, Precedence: 20, Handler: OrOperator}
-var And = &OperationType{Type: "AND", NumArgs: 2, Precedence: 20, Handler: AndOperator}
+var orOpType = &operationType{Type: "OR", NumArgs: 2, Precedence: 20, Handler: orOperator}
+var andOpType = &operationType{Type: "AND", NumArgs: 2, Precedence: 20, Handler: andOperator}

-var Union = &OperationType{Type: "UNION", NumArgs: 2, Precedence: 10, Handler: UnionOperator}
+var unionOpType = &operationType{Type: "UNION", NumArgs: 2, Precedence: 10, Handler: unionOperator}

-var Pipe = &OperationType{Type: "PIPE", NumArgs: 2, Precedence: 30, Handler: PipeOperator}
+var pipeOpType = &operationType{Type: "PIPE", NumArgs: 2, Precedence: 30, Handler: pipeOperator}

-var Assign = &OperationType{Type: "ASSIGN", NumArgs: 2, Precedence: 40, Handler: AssignUpdateOperator}
-var AddAssign = &OperationType{Type: "ADD_ASSIGN", NumArgs: 2, Precedence: 40, Handler: AddAssignOperator}
+var assignOpType = &operationType{Type: "ASSIGN", NumArgs: 2, Precedence: 40, Handler: assignUpdateOperator}
+var addAssignOpType = &operationType{Type: "ADD_ASSIGN", NumArgs: 2, Precedence: 40, Handler: addAssignOperator}

-var AssignAttributes = &OperationType{Type: "ASSIGN_ATTRIBUTES", NumArgs: 2, Precedence: 40, Handler: AssignAttributesOperator}
-var AssignStyle = &OperationType{Type: "ASSIGN_STYLE", NumArgs: 2, Precedence: 40, Handler: AssignStyleOperator}
-var AssignTag = &OperationType{Type: "ASSIGN_TAG", NumArgs: 2, Precedence: 40, Handler: AssignTagOperator}
-var AssignComment = &OperationType{Type: "ASSIGN_COMMENT", NumArgs: 2, Precedence: 40, Handler: AssignCommentsOperator}
-var AssignAnchor = &OperationType{Type: "ASSIGN_ANCHOR", NumArgs: 2, Precedence: 40, Handler: AssignAnchorOperator}
-var AssignAlias = &OperationType{Type: "ASSIGN_ALIAS", NumArgs: 2, Precedence: 40, Handler: AssignAliasOperator}
+var assignAttributesOpType = &operationType{Type: "ASSIGN_ATTRIBUTES", NumArgs: 2, Precedence: 40, Handler: assignAttributesOperator}
+var assignStyleOpType = &operationType{Type: "ASSIGN_STYLE", NumArgs: 2, Precedence: 40, Handler: assignStyleOperator}
+var assignTagOpType = &operationType{Type: "ASSIGN_TAG", NumArgs: 2, Precedence: 40, Handler: assignTagOperator}
+var assignCommentOpType = &operationType{Type: "ASSIGN_COMMENT", NumArgs: 2, Precedence: 40, Handler: assignCommentsOperator}
+var assignAnchorOpType = &operationType{Type: "ASSIGN_ANCHOR", NumArgs: 2, Precedence: 40, Handler: assignAnchorOperator}
+var assignAliasOpType = &operationType{Type: "ASSIGN_ALIAS", NumArgs: 2, Precedence: 40, Handler: assignAliasOperator}

-var Multiply = &OperationType{Type: "MULTIPLY", NumArgs: 2, Precedence: 45, Handler: MultiplyOperator}
-var Add = &OperationType{Type: "ADD", NumArgs: 2, Precedence: 45, Handler: AddOperator}
-var Alternative = &OperationType{Type: "ALTERNATIVE", NumArgs: 2, Precedence: 45, Handler: AlternativeOperator}
+var multiplyOpType = &operationType{Type: "MULTIPLY", NumArgs: 2, Precedence: 45, Handler: multiplyOperator}
+var addOpType = &operationType{Type: "ADD", NumArgs: 2, Precedence: 45, Handler: addOperator}
+var alternativeOpType = &operationType{Type: "ALTERNATIVE", NumArgs: 2, Precedence: 45, Handler: alternativeOperator}

-var Equals = &OperationType{Type: "EQUALS", NumArgs: 2, Precedence: 40, Handler: EqualsOperator}
-var CreateMap = &OperationType{Type: "CREATE_MAP", NumArgs: 2, Precedence: 40, Handler: CreateMapOperator}
+var equalsOpType = &operationType{Type: "EQUALS", NumArgs: 2, Precedence: 40, Handler: equalsOperator}
+var createMapOpType = &operationType{Type: "CREATE_MAP", NumArgs: 2, Precedence: 40, Handler: createMapOperator}

-var ShortPipe = &OperationType{Type: "SHORT_PIPE", NumArgs: 2, Precedence: 45, Handler: PipeOperator}
+var shortPipeOpType = &operationType{Type: "SHORT_PIPE", NumArgs: 2, Precedence: 45, Handler: pipeOperator}

-var Length = &OperationType{Type: "LENGTH", NumArgs: 0, Precedence: 50, Handler: LengthOperator}
-var Collect = &OperationType{Type: "COLLECT", NumArgs: 0, Precedence: 50, Handler: CollectOperator}
-var GetStyle = &OperationType{Type: "GET_STYLE", NumArgs: 0, Precedence: 50, Handler: GetStyleOperator}
-var GetTag = &OperationType{Type: "GET_TAG", NumArgs: 0, Precedence: 50, Handler: GetTagOperator}
-var GetComment = &OperationType{Type: "GET_COMMENT", NumArgs: 0, Precedence: 50, Handler: GetCommentsOperator}
-var GetAnchor = &OperationType{Type: "GET_ANCHOR", NumArgs: 0, Precedence: 50, Handler: GetAnchorOperator}
-var GetAlias = &OperationType{Type: "GET_ALIAS", NumArgs: 0, Precedence: 50, Handler: GetAliasOperator}
-var GetDocumentIndex = &OperationType{Type: "GET_DOCUMENT_INDEX", NumArgs: 0, Precedence: 50, Handler: GetDocumentIndexOperator}
-var GetFilename = &OperationType{Type: "GET_FILENAME", NumArgs: 0, Precedence: 50, Handler: GetFilenameOperator}
-var GetFileIndex = &OperationType{Type: "GET_FILE_INDEX", NumArgs: 0, Precedence: 50, Handler: GetFileIndexOperator}
-var GetPath = &OperationType{Type: "GET_PATH", NumArgs: 0, Precedence: 50, Handler: GetPathOperator}
+var lengthOpType = &operationType{Type: "LENGTH", NumArgs: 0, Precedence: 50, Handler: lengthOperator}
+var collectOpType = &operationType{Type: "COLLECT", NumArgs: 0, Precedence: 50, Handler: collectOperator}
+var getStyleOpType = &operationType{Type: "GET_STYLE", NumArgs: 0, Precedence: 50, Handler: getStyleOperator}
+var getTagOpType = &operationType{Type: "GET_TAG", NumArgs: 0, Precedence: 50, Handler: getTagOperator}
+var getCommentOpType = &operationType{Type: "GET_COMMENT", NumArgs: 0, Precedence: 50, Handler: getCommentsOperator}
+var getAnchorOpType = &operationType{Type: "GET_ANCHOR", NumArgs: 0, Precedence: 50, Handler: getAnchorOperator}
+var getAliasOptype = &operationType{Type: "GET_ALIAS", NumArgs: 0, Precedence: 50, Handler: getAliasOperator}
+var getDocumentIndexOpType = &operationType{Type: "GET_DOCUMENT_INDEX", NumArgs: 0, Precedence: 50, Handler: getDocumentIndexOperator}
+var getFilenameOpType = &operationType{Type: "GET_FILENAME", NumArgs: 0, Precedence: 50, Handler: getFilenameOperator}
+var getFileIndexOpType = &operationType{Type: "GET_FILE_INDEX", NumArgs: 0, Precedence: 50, Handler: getFileIndexOperator}
+var getPathOpType = &operationType{Type: "GET_PATH", NumArgs: 0, Precedence: 50, Handler: getPathOperator}

-var Explode = &OperationType{Type: "EXPLODE", NumArgs: 1, Precedence: 50, Handler: ExplodeOperator}
-var SortKeys = &OperationType{Type: "SORT_KEYS", NumArgs: 1, Precedence: 50, Handler: SortKeysOperator}
+var explodeOpType = &operationType{Type: "EXPLODE", NumArgs: 1, Precedence: 50, Handler: explodeOperator}
+var sortKeysOpType = &operationType{Type: "SORT_KEYS", NumArgs: 1, Precedence: 50, Handler: sortKeysOperator}

-var CollectObject = &OperationType{Type: "COLLECT_OBJECT", NumArgs: 0, Precedence: 50, Handler: CollectObjectOperator}
-var TraversePath = &OperationType{Type: "TRAVERSE_PATH", NumArgs: 0, Precedence: 50, Handler: TraversePathOperator}
-var TraverseArray = &OperationType{Type: "TRAVERSE_ARRAY", NumArgs: 1, Precedence: 50, Handler: TraverseArrayOperator}
+var collectObjectOpType = &operationType{Type: "COLLECT_OBJECT", NumArgs: 0, Precedence: 50, Handler: collectObjectOperator}
+var traversePathOpType = &operationType{Type: "TRAVERSE_PATH", NumArgs: 0, Precedence: 50, Handler: traversePathOperator}
+var traverseArrayOpType = &operationType{Type: "TRAVERSE_ARRAY", NumArgs: 1, Precedence: 50, Handler: traverseArrayOperator}

-var DocumentFilter = &OperationType{Type: "DOCUMENT_FILTER", NumArgs: 0, Precedence: 50, Handler: TraversePathOperator}
-var SelfReference = &OperationType{Type: "SELF", NumArgs: 0, Precedence: 50, Handler: SelfOperator}
-var ValueOp = &OperationType{Type: "VALUE", NumArgs: 0, Precedence: 50, Handler: ValueOperator}
-var Not = &OperationType{Type: "NOT", NumArgs: 0, Precedence: 50, Handler: NotOperator}
-var Empty = &OperationType{Type: "EMPTY", NumArgs: 50, Handler: EmptyOperator}
+var documentFilterOpType = &operationType{Type: "DOCUMENT_FILTER", NumArgs: 0, Precedence: 50, Handler: traversePathOperator}
+var selfReferenceOpType = &operationType{Type: "SELF", NumArgs: 0, Precedence: 50, Handler: selfOperator}
+var valueOpType = &operationType{Type: "VALUE", NumArgs: 0, Precedence: 50, Handler: valueOperator}
+var envOpType = &operationType{Type: "ENV", NumArgs: 0, Precedence: 50, Handler: envOperator}
+var notOpType = &operationType{Type: "NOT", NumArgs: 0, Precedence: 50, Handler: notOperator}
+var emptyOpType = &operationType{Type: "EMPTY", NumArgs: 50, Handler: emptyOperator}

-var RecursiveDescent = &OperationType{Type: "RECURSIVE_DESCENT", NumArgs: 0, Precedence: 50, Handler: RecursiveDescentOperator}
+var recursiveDescentOpType = &operationType{Type: "RECURSIVE_DESCENT", NumArgs: 0, Precedence: 50, Handler: recursiveDescentOperator}

-var Select = &OperationType{Type: "SELECT", NumArgs: 1, Precedence: 50, Handler: SelectOperator}
-var Has = &OperationType{Type: "HAS", NumArgs: 1, Precedence: 50, Handler: HasOperator}
-var DeleteChild = &OperationType{Type: "DELETE", NumArgs: 1, Precedence: 40, Handler: DeleteChildOperator}
-var DeleteImmediateChild = &OperationType{Type: "DELETE_IMMEDIATE_CHILD", NumArgs: 1, Precedence: 40, Handler: DeleteImmediateChildOperator}
+var selectOpType = &operationType{Type: "SELECT", NumArgs: 1, Precedence: 50, Handler: selectOperator}
+var hasOpType = &operationType{Type: "HAS", NumArgs: 1, Precedence: 50, Handler: hasOperator}
+var deleteChildOpType = &operationType{Type: "DELETE", NumArgs: 1, Precedence: 40, Handler: deleteChildOperator}
+var deleteImmediateChildOpType = &operationType{Type: "DELETE_IMMEDIATE_CHILD", NumArgs: 1, Precedence: 40, Handler: deleteImmediateChildOperator}

 type Operation struct {
-	OperationType *OperationType
+	OperationType *operationType
 	Value         interface{}
 	StringValue   string
 	CandidateNode *CandidateNode // used for Value Path elements
 	Preferences   interface{}
-	UpdateAssign  bool // used for assign ops, when true it means we evaluate the rhs given the lhs (instead of matching nodes)
+	UpdateAssign  bool // used for assign ops, when true it means we evaluate the rhs given the lhs
 }

-func CreateValueOperation(value interface{}, stringValue string) *Operation {
+func createValueOperation(value interface{}, stringValue string) *Operation {
 	var node yaml.Node = yaml.Node{Kind: yaml.ScalarNode}
 	node.Value = stringValue

@@ -107,7 +109,7 @@ func CreateValueOperation(value interface{}, stringValue string) *Operation {
 	}

 	return &Operation{
-		OperationType: ValueOp,
+		OperationType: valueOpType,
 		Value:         value,
 		StringValue:   stringValue,
 		CandidateNode: &CandidateNode{Node: &node},
@@ -116,13 +118,13 @@ func CreateValueOperation(value interface{}, stringValue string) *Operation {

 // debugging purposes only
 func (p *Operation) toString() string {
-	if p.OperationType == TraversePath {
+	if p.OperationType == traversePathOpType {
 		return fmt.Sprintf("%v", p.Value)
-	} else if p.OperationType == DocumentFilter {
+	} else if p.OperationType == documentFilterOpType {
 		return fmt.Sprintf("d%v", p.Value)
-	} else if p.OperationType == SelfReference {
+	} else if p.OperationType == selfReferenceOpType {
 		return "SELF"
-	} else if p.OperationType == ValueOp {
+	} else if p.OperationType == valueOpType {
 		return fmt.Sprintf("%v (%T)", p.Value, p.Value)
 	} else {
 		return fmt.Sprintf("%v", p.OperationType.Type)
--- a/pkg/yqlib/matchKeyString.go
+++ b/pkg/yqlib/matchKeyString.go
@@ -1,6 +1,6 @@
 package yqlib

-func Match(name string, pattern string) (matched bool) {
+func matchKey(name string, pattern string) (matched bool) {
 	if pattern == "" {
 		return name == pattern
 	}
--- a/pkg/yqlib/operator_add.go
+++ b/pkg/yqlib/operator_add.go
@@ -4,21 +4,22 @@ import (
 	"fmt"

 	"container/list"
+	"strconv"

 	yaml "gopkg.in/yaml.v3"
 )

-func createSelfAddOp(rhs *PathTreeNode) *PathTreeNode {
-	return &PathTreeNode{Operation: &Operation{OperationType: Add},
-		Lhs: &PathTreeNode{Operation: &Operation{OperationType: SelfReference}},
+func createAddOp(lhs *ExpressionNode, rhs *ExpressionNode) *ExpressionNode {
+	return &ExpressionNode{Operation: &Operation{OperationType: addOpType},
+		Lhs: lhs,
 		Rhs: rhs}
 }

-func AddAssignOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
-	assignmentOp := &Operation{OperationType: Assign}
-	assignmentOp.UpdateAssign = true
+func addAssignOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
+	assignmentOp := &Operation{OperationType: assignOpType}
+	assignmentOp.UpdateAssign = false

-	assignmentOpNode := &PathTreeNode{Operation: assignmentOp, Lhs: pathNode.Lhs, Rhs: createSelfAddOp(pathNode.Rhs)}
+	assignmentOpNode := &ExpressionNode{Operation: assignmentOp, Lhs: expressionNode.Lhs, Rhs: createAddOp(expressionNode.Lhs, expressionNode.Rhs)}
 	return d.GetMatchingNodes(matchingNodes, assignmentOpNode)
 }

@@ -36,22 +37,17 @@ func toNodes(candidate *CandidateNode) []*yaml.Node {

 }

-func AddOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func addOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("Add operator")

-	return crossFunction(d, matchingNodes, pathNode, add)
+	return crossFunction(d, matchingNodes, expressionNode, add)
 }

 func add(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
-	lhs.Node = UnwrapDoc(lhs.Node)
-	rhs.Node = UnwrapDoc(rhs.Node)
+	lhs.Node = unwrapDoc(lhs.Node)
+	rhs.Node = unwrapDoc(rhs.Node)

-	target := &CandidateNode{
-		Path:     lhs.Path,
-		Document: lhs.Document,
-		Filename: lhs.Filename,
-		Node:     &yaml.Node{},
-	}
+	target := lhs.CreateChild(nil, &yaml.Node{})
 	lhsNode := lhs.Node

 	switch lhsNode.Kind {
@@ -63,7 +59,48 @@ func add(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*Candida
 		target.Node.Tag = "!!seq"
 		target.Node.Content = append(lhsNode.Content, toNodes(rhs)...)
 	case yaml.ScalarNode:
-		return nil, fmt.Errorf("Scalars not yet supported for addition")
+		if rhs.Node.Kind != yaml.ScalarNode {
+			return nil, fmt.Errorf("%v (%v) cannot be added to a %v", rhs.Node.Tag, rhs.Path, lhsNode.Tag)
+		}
+		target.Node.Kind = yaml.ScalarNode
+		target.Node.Style = lhsNode.Style
+		return addScalars(target, lhsNode, rhs.Node)
+	}
+
+	return target, nil
+}
+
+func addScalars(target *CandidateNode, lhs *yaml.Node, rhs *yaml.Node) (*CandidateNode, error) {
+
+	if lhs.Tag == "!!str" {
+		target.Node.Tag = "!!str"
+		target.Node.Value = lhs.Value + rhs.Value
+	} else if lhs.Tag == "!!int" && rhs.Tag == "!!int" {
+		lhsNum, err := strconv.Atoi(lhs.Value)
+		if err != nil {
+			return nil, err
+		}
+		rhsNum, err := strconv.Atoi(rhs.Value)
+		if err != nil {
+			return nil, err
+		}
+		sum := lhsNum + rhsNum
+		target.Node.Tag = "!!int"
+		target.Node.Value = fmt.Sprintf("%v", sum)
+	} else if (lhs.Tag == "!!int" || lhs.Tag == "!!float") && (rhs.Tag == "!!int" || rhs.Tag == "!!float") {
+		lhsNum, err := strconv.ParseFloat(lhs.Value, 64)
+		if err != nil {
+			return nil, err
+		}
+		rhsNum, err := strconv.ParseFloat(rhs.Value, 64)
+		if err != nil {
+			return nil, err
+		}
+		sum := lhsNum + rhsNum
+		target.Node.Tag = "!!float"
+		target.Node.Value = fmt.Sprintf("%v", sum)
+	} else {
+		return nil, fmt.Errorf("%v cannot be added to %v", lhs.Tag, rhs.Tag)
 	}

 	return target, nil
--- a/pkg/yqlib/operator_add_test.go
+++ b/pkg/yqlib/operator_add_test.go
@@ -38,11 +38,11 @@ var addOperatorScenarios = []expressionScenario{
 		},
 	},
 	{
-		description: "Add object to array",
-		document:    `{a: [1,2], c: {cat: meow}}`,
-		expression:  `.a + .c`,
+		description: "Add new object to array",
+		document:    `a: [{dog: woof}]`,
+		expression:  `.a + {"cat": "meow"}`,
 		expected: []string{
-			"D0, P[a], (!!seq)::[1, 2, {cat: meow}]\n",
+			"D0, P[a], (!!seq)::[{dog: woof}, {cat: meow}]\n",
 		},
 	},
 	{
@@ -61,6 +61,48 @@ var addOperatorScenarios = []expressionScenario{
 			"D0, P[], (doc)::{a: [1, 2, 3, 4], b: [3, 4]}\n",
 		},
 	},
+	{
+		description: "String concatenation",
+		document:    `{a: cat, b: meow}`,
+		expression:  `.a = .a + .b`,
+		expected: []string{
+			"D0, P[], (doc)::{a: catmeow, b: meow}\n",
+		},
+	},
+	{
+		description: "Relative string concatenation",
+		document:    `{a: cat, b: meow}`,
+		expression:  `.a += .b`,
+		expected: []string{
+			"D0, P[], (doc)::{a: catmeow, b: meow}\n",
+		},
+	},
+	{
+		description:    "Number addition - float",
+		subdescription: "If the lhs or rhs are floats then the expression will be calculated with floats.",
+		document:       `{a: 3, b: 4.9}`,
+		expression:     `.a = .a + .b`,
+		expected: []string{
+			"D0, P[], (doc)::{a: 7.9, b: 4.9}\n",
+		},
+	},
+	{
+		description:    "Number addition - int",
+		subdescription: "If both the lhs and rhs are ints then the expression will be calculated with ints.",
+		document:       `{a: 3, b: 4}`,
+		expression:     `.a = .a + .b`,
+		expected: []string{
+			"D0, P[], (doc)::{a: 7, b: 4}\n",
+		},
+	},
+	{
+		description: "Increment number",
+		document:    `{a: 3}`,
+		expression:  `.a += 1`,
+		expected: []string{
+			"D0, P[], (doc)::{a: 4}\n",
+		},
+	},
 }

 func TestAddOperatorScenarios(t *testing.T) {
--- a/pkg/yqlib/operator_alternative.go
+++ b/pkg/yqlib/operator_alternative.go
@@ -7,14 +7,14 @@ import (
 // corssFunction no matches
 // can boolean use crossfunction

-func AlternativeOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func alternativeOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("-- alternative")
-	return crossFunction(d, matchingNodes, pathNode, alternativeFunc)
+	return crossFunction(d, matchingNodes, expressionNode, alternativeFunc)
 }

 func alternativeFunc(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
-	lhs.Node = UnwrapDoc(lhs.Node)
-	rhs.Node = UnwrapDoc(rhs.Node)
+	lhs.Node = unwrapDoc(lhs.Node)
+	rhs.Node = unwrapDoc(rhs.Node)
 	log.Debugf("Alternative LHS: %v", lhs.Node.Tag)
 	log.Debugf("-          RHS: %v", rhs.Node.Tag)

--- a/pkg/yqlib/operator_anchors_aliases.go
+++ b/pkg/yqlib/operator_anchors_aliases.go
@@ -6,13 +6,13 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )

-func AssignAliasOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func assignAliasOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {

 	log.Debugf("AssignAlias operator!")

 	aliasName := ""
-	if !pathNode.Operation.UpdateAssign {
-		rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+	if !expressionNode.Operation.UpdateAssign {
+		rhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Rhs)
 		if err != nil {
 			return nil, err
 		}
@@ -21,7 +21,7 @@ func AssignAliasOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNod
 		}
 	}

-	lhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Lhs)
+	lhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Lhs)

 	if err != nil {
 		return nil, err
@@ -31,8 +31,8 @@ func AssignAliasOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNod
 		candidate := el.Value.(*CandidateNode)
 		log.Debugf("Setting aliasName : %v", candidate.GetKey())

-		if pathNode.Operation.UpdateAssign {
-			rhs, err := d.GetMatchingNodes(nodeToMap(candidate), pathNode.Rhs)
+		if expressionNode.Operation.UpdateAssign {
+			rhs, err := d.GetMatchingNodes(nodeToMap(candidate), expressionNode.Rhs)
 			if err != nil {
 				return nil, err
 			}
@@ -47,26 +47,26 @@ func AssignAliasOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNod
 	return matchingNodes, nil
 }

-func GetAliasOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func getAliasOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("GetAlias operator!")
 	var results = list.New()

 	for el := matchingNodes.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
 		node := &yaml.Node{Kind: yaml.ScalarNode, Value: candidate.Node.Value, Tag: "!!str"}
-		lengthCand := &CandidateNode{Node: node, Document: candidate.Document, Path: candidate.Path}
-		results.PushBack(lengthCand)
+		result := candidate.CreateChild(nil, node)
+		results.PushBack(result)
 	}
 	return results, nil
 }

-func AssignAnchorOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func assignAnchorOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {

 	log.Debugf("AssignAnchor operator!")

 	anchorName := ""
-	if !pathNode.Operation.UpdateAssign {
-		rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+	if !expressionNode.Operation.UpdateAssign {
+		rhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Rhs)
 		if err != nil {
 			return nil, err
 		}
@@ -76,7 +76,7 @@ func AssignAnchorOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNo
 		}
 	}

-	lhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Lhs)
+	lhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Lhs)

 	if err != nil {
 		return nil, err
@@ -86,8 +86,8 @@ func AssignAnchorOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNo
 		candidate := el.Value.(*CandidateNode)
 		log.Debugf("Setting anchorName of : %v", candidate.GetKey())

-		if pathNode.Operation.UpdateAssign {
-			rhs, err := d.GetMatchingNodes(nodeToMap(candidate), pathNode.Rhs)
+		if expressionNode.Operation.UpdateAssign {
+			rhs, err := d.GetMatchingNodes(nodeToMap(candidate), expressionNode.Rhs)
 			if err != nil {
 				return nil, err
 			}
@@ -102,7 +102,7 @@ func AssignAnchorOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNo
 	return matchingNodes, nil
 }

-func GetAnchorOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func getAnchorOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("GetAnchor operator!")
 	var results = list.New()

@@ -110,19 +110,19 @@ func GetAnchorOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode
 		candidate := el.Value.(*CandidateNode)
 		anchor := candidate.Node.Anchor
 		node := &yaml.Node{Kind: yaml.ScalarNode, Value: anchor, Tag: "!!str"}
-		lengthCand := &CandidateNode{Node: node, Document: candidate.Document, Path: candidate.Path}
-		results.PushBack(lengthCand)
+		result := candidate.CreateChild(nil, node)
+		results.PushBack(result)
 	}
 	return results, nil
 }

-func ExplodeOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func explodeOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("-- ExplodeOperation")

 	for el := matchMap.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)

-		rhs, err := d.GetMatchingNodes(nodeToMap(candidate), pathNode.Rhs)
+		rhs, err := d.GetMatchingNodes(nodeToMap(candidate), expressionNode.Rhs)

 		if err != nil {
 			return nil, err
--- a/pkg/yqlib/operator_assign.go
+++ b/pkg/yqlib/operator_assign.go
@@ -2,21 +2,21 @@ package yqlib

 import "container/list"

-func AssignUpdateOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
-	lhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Lhs)
+func assignUpdateOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
+	lhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Lhs)
 	if err != nil {
 		return nil, err
 	}
 	var rhs *list.List
-	if !pathNode.Operation.UpdateAssign {
-		rhs, err = d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+	if !expressionNode.Operation.UpdateAssign {
+		rhs, err = d.GetMatchingNodes(matchingNodes, expressionNode.Rhs)
 	}

 	for el := lhs.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)

-		if pathNode.Operation.UpdateAssign {
-			rhs, err = d.GetMatchingNodes(nodeToMap(candidate), pathNode.Rhs)
+		if expressionNode.Operation.UpdateAssign {
+			rhs, err = d.GetMatchingNodes(nodeToMap(candidate), expressionNode.Rhs)
 		}

 		if err != nil {
@@ -28,28 +28,24 @@ func AssignUpdateOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNo

 		if first != nil {
 			rhsCandidate := first.Value.(*CandidateNode)
-			rhsCandidate.Node = UnwrapDoc(rhsCandidate.Node)
+			rhsCandidate.Node = unwrapDoc(rhsCandidate.Node)
 			candidate.UpdateFrom(rhsCandidate)
 		}
 	}
-	// // if there was nothing given, perhaps we are creating a new yaml doc
-	// if matchingNodes.Len() == 0 {
-	// 	log.Debug("started with nothing, returning LHS, %v", lhs.Len())
-	// 	return lhs, nil
-	// }
+
 	return matchingNodes, nil
 }

 // does not update content or values
-func AssignAttributesOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
-	lhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Lhs)
+func assignAttributesOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
+	lhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Lhs)
 	if err != nil {
 		return nil, err
 	}
 	for el := lhs.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)

-		rhs, err := d.GetMatchingNodes(nodeToMap(candidate), pathNode.Rhs)
+		rhs, err := d.GetMatchingNodes(nodeToMap(candidate), expressionNode.Rhs)

 		if err != nil {
 			return nil, err
--- a/pkg/yqlib/operator_booleans.go
+++ b/pkg/yqlib/operator_booleans.go
@@ -7,7 +7,7 @@ import (
 )

 func isTruthy(c *CandidateNode) (bool, error) {
-	node := UnwrapDoc(c.Node)
+	node := unwrapDoc(c.Node)
 	value := true

 	if node.Tag == "!!null" {
@@ -27,8 +27,8 @@ type boolOp func(bool, bool) bool

 func performBoolOp(op boolOp) func(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
 	return func(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
-		lhs.Node = UnwrapDoc(lhs.Node)
-		rhs.Node = UnwrapDoc(rhs.Node)
+		lhs.Node = unwrapDoc(lhs.Node)
+		rhs.Node = unwrapDoc(rhs.Node)

 		lhsTrue, errDecoding := isTruthy(lhs)
 		if errDecoding != nil {
@@ -44,23 +44,23 @@ func performBoolOp(op boolOp) func(d *dataTreeNavigator, lhs *CandidateNode, rhs
 	}
 }

-func OrOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func orOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("-- orOp")
-	return crossFunction(d, matchingNodes, pathNode, performBoolOp(
+	return crossFunction(d, matchingNodes, expressionNode, performBoolOp(
 		func(b1 bool, b2 bool) bool {
 			return b1 || b2
 		}))
 }

-func AndOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func andOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("-- AndOp")
-	return crossFunction(d, matchingNodes, pathNode, performBoolOp(
+	return crossFunction(d, matchingNodes, expressionNode, performBoolOp(
 		func(b1 bool, b2 bool) bool {
 			return b1 && b2
 		}))
 }

-func NotOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func notOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("-- notOperation")
 	var results = list.New()

--- a/pkg/yqlib/operator_collect.go
+++ b/pkg/yqlib/operator_collect.go
@@ -6,7 +6,7 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )

-func CollectOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func collectOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("-- collectOperation")

 	if matchMap.Len() == 0 {
@@ -18,21 +18,22 @@ func CollectOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *PathTr
 	var results = list.New()

 	node := &yaml.Node{Kind: yaml.SequenceNode, Tag: "!!seq"}
-
-	var document uint = 0
-	var path []interface{}
+	var collectC *CandidateNode
+	if matchMap.Front() != nil {
+		collectC = matchMap.Front().Value.(*CandidateNode).CreateChild(nil, node)
+		if len(collectC.Path) > 0 {
+			collectC.Path = collectC.Path[:len(collectC.Path)-1]
+		}
+	} else {
+		collectC = &CandidateNode{Node: node}
+	}

 	for el := matchMap.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
 		log.Debugf("Collecting %v", NodeToString(candidate))
-		if path == nil && candidate.Path != nil && len(candidate.Path) > 1 {
-			path = candidate.Path[:len(candidate.Path)-1]
-			document = candidate.Document
-		}
-		node.Content = append(node.Content, candidate.Node)
+		node.Content = append(node.Content, unwrapDoc(candidate.Node))
 	}

-	collectC := &CandidateNode{Node: node, Document: document, Path: path}
 	results.PushBack(collectC)

 	return results, nil
--- a/pkg/yqlib/operator_collect_object.go
+++ b/pkg/yqlib/operator_collect_object.go
@@ -17,7 +17,7 @@ import (
 ...
 */

-func CollectObjectOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func collectObjectOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("-- collectObjectOperation")

 	if matchMap.Len() == 0 {
@@ -35,7 +35,7 @@ func CollectObjectOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *
 	for el := matchMap.Front(); el != nil; el = el.Next() {
 		candidateNode := el.Value.(*CandidateNode)
 		for i := 0; i < len(first.Node.Content); i++ {
-			rotated[i].PushBack(createChildCandidate(candidateNode, i))
+			rotated[i].PushBack(candidateNode.CreateChild(i, candidateNode.Node.Content[i]))
 		}
 	}

@@ -52,15 +52,6 @@ func CollectObjectOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *

 }

-func createChildCandidate(candidate *CandidateNode, index int) *CandidateNode {
-	return &CandidateNode{
-		Document: candidate.Document,
-		Path:     candidate.CreateChildPath(index),
-		Filename: candidate.Filename,
-		Node:     candidate.Node.Content[index],
-	}
-}
-
 func collect(d *dataTreeNavigator, aggregate *list.List, remainingMatches *list.List) (*list.List, error) {
 	if remainingMatches.Len() == 0 {
 		return aggregate, nil
@@ -68,8 +59,8 @@ func collect(d *dataTreeNavigator, aggregate *list.List, remainingMatches *list.

 	candidate := remainingMatches.Remove(remainingMatches.Front()).(*CandidateNode)

-	splatted, err := Splat(d, nodeToMap(candidate),
-		&TraversePreferences{FollowAlias: false, IncludeMapKeys: false})
+	splatted, err := splat(d, nodeToMap(candidate),
+		&traversePreferences{FollowAlias: false, IncludeMapKeys: false})

 	for splatEl := splatted.Front(); splatEl != nil; splatEl = splatEl.Next() {
 		splatEl.Value.(*CandidateNode).Path = nil
@@ -96,7 +87,7 @@ func collect(d *dataTreeNavigator, aggregate *list.List, remainingMatches *list.

 			newCandidate.Path = nil

-			newCandidate, err = multiply(&MultiplyPreferences{AppendArrays: false})(d, newCandidate, splatCandidate)
+			newCandidate, err = multiply(&multiplyPreferences{AppendArrays: false})(d, newCandidate, splatCandidate)
 			if err != nil {
 				return nil, err
 			}
--- a/pkg/yqlib/operator_collect_test.go
+++ b/pkg/yqlib/operator_collect_test.go
@@ -13,6 +13,15 @@ var collectOperatorScenarios = []expressionScenario{
 			"D0, P[], (!!seq)::[]\n",
 		},
 	},
+	{
+		skipDoc:  true,
+		document: "{a: apple}\n---\n{b: frog}",
+
+		expression: `[.]`,
+		expected: []string{
+			"D0, P[], (!!seq)::- {a: apple}\n- {b: frog}\n",
+		},
+	},
 	{
 		skipDoc:    true,
 		document:   ``,
--- a/pkg/yqlib/operator_comments.go
+++ b/pkg/yqlib/operator_comments.go
@@ -7,27 +7,27 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )

-type CommentOpPreferences struct {
+type commentOpPreferences struct {
 	LineComment bool
 	HeadComment bool
 	FootComment bool
 }

-func AssignCommentsOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func assignCommentsOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {

 	log.Debugf("AssignComments operator!")

-	lhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Lhs)
+	lhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Lhs)

 	if err != nil {
 		return nil, err
 	}

-	preferences := pathNode.Operation.Preferences.(*CommentOpPreferences)
+	preferences := expressionNode.Operation.Preferences.(*commentOpPreferences)

 	comment := ""
-	if !pathNode.Operation.UpdateAssign {
-		rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+	if !expressionNode.Operation.UpdateAssign {
+		rhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Rhs)
 		if err != nil {
 			return nil, err
 		}
@@ -40,8 +40,8 @@ func AssignCommentsOperator(d *dataTreeNavigator, matchingNodes *list.List, path
 	for el := lhs.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)

-		if pathNode.Operation.UpdateAssign {
-			rhs, err := d.GetMatchingNodes(nodeToMap(candidate), pathNode.Rhs)
+		if expressionNode.Operation.UpdateAssign {
+			rhs, err := d.GetMatchingNodes(nodeToMap(candidate), expressionNode.Rhs)
 			if err != nil {
 				return nil, err
 			}
@@ -66,8 +66,8 @@ func AssignCommentsOperator(d *dataTreeNavigator, matchingNodes *list.List, path
 	return matchingNodes, nil
 }

-func GetCommentsOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
-	preferences := pathNode.Operation.Preferences.(*CommentOpPreferences)
+func getCommentsOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
+	preferences := expressionNode.Operation.Preferences.(*commentOpPreferences)
 	log.Debugf("GetComments operator!")
 	var results = list.New()

@@ -84,8 +84,8 @@ func GetCommentsOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNod
 		comment = strings.Replace(comment, "# ", "", 1)

 		node := &yaml.Node{Kind: yaml.ScalarNode, Value: comment, Tag: "!!str"}
-		lengthCand := &CandidateNode{Node: node, Document: candidate.Document, Path: candidate.Path}
-		results.PushBack(lengthCand)
+		result := candidate.CreateChild(nil, node)
+		results.PushBack(result)
 	}
 	return results, nil
 }
--- a/pkg/yqlib/operator_create_map.go
+++ b/pkg/yqlib/operator_create_map.go
@@ -6,7 +6,7 @@ import (
 	"gopkg.in/yaml.v3"
 )

-func CreateMapOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func createMapOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("-- createMapOperation")

 	//each matchingNodes entry should turn into a sequence of keys to create.
@@ -22,14 +22,14 @@ func CreateMapOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode

 		for matchingNodeEl := matchingNodes.Front(); matchingNodeEl != nil; matchingNodeEl = matchingNodeEl.Next() {
 			matchingNode := matchingNodeEl.Value.(*CandidateNode)
-			sequenceNode, err := sequenceFor(d, matchingNode, pathNode)
+			sequenceNode, err := sequenceFor(d, matchingNode, expressionNode)
 			if err != nil {
 				return nil, err
 			}
 			sequences.PushBack(sequenceNode)
 		}
 	} else {
-		sequenceNode, err := sequenceFor(d, nil, pathNode)
+		sequenceNode, err := sequenceFor(d, nil, expressionNode)
 		if err != nil {
 			return nil, err
 		}
@@ -40,7 +40,7 @@ func CreateMapOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode

 }

-func sequenceFor(d *dataTreeNavigator, matchingNode *CandidateNode, pathNode *PathTreeNode) (*CandidateNode, error) {
+func sequenceFor(d *dataTreeNavigator, matchingNode *CandidateNode, expressionNode *ExpressionNode) (*CandidateNode, error) {
 	var path []interface{}
 	var document uint = 0
 	var matches = list.New()
@@ -51,14 +51,14 @@ func sequenceFor(d *dataTreeNavigator, matchingNode *CandidateNode, pathNode *Pa
 		matches = nodeToMap(matchingNode)
 	}

-	mapPairs, err := crossFunction(d, matches, pathNode,
+	mapPairs, err := crossFunction(d, matches, expressionNode,
 		func(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
 			node := yaml.Node{Kind: yaml.MappingNode, Tag: "!!map"}
 			log.Debugf("LHS:", NodeToString(lhs))
 			log.Debugf("RHS:", NodeToString(rhs))
 			node.Content = []*yaml.Node{
-				UnwrapDoc(lhs.Node),
-				UnwrapDoc(rhs.Node),
+				unwrapDoc(lhs.Node),
+				unwrapDoc(rhs.Node),
 			}

 			return &CandidateNode{Node: &node, Document: document, Path: path}, nil
--- a/pkg/yqlib/operator_delete.go
+++ b/pkg/yqlib/operator_delete.go
@@ -7,9 +7,9 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )

-func DeleteChildOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func deleteChildOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {

-	nodesToDelete, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+	nodesToDelete, err := d.GetMatchingNodes(matchingNodes, expressionNode.Rhs)

 	if err != nil {
 		return nil, err
@@ -19,11 +19,11 @@ func DeleteChildOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNod
 		candidate := el.Value.(*CandidateNode)

 		deleteImmediateChildOp := &Operation{
-			OperationType: DeleteImmediateChild,
+			OperationType: deleteImmediateChildOpType,
 			Value:         candidate.Path[len(candidate.Path)-1],
 		}

-		deleteImmediateChildOpNode := &PathTreeNode{
+		deleteImmediateChildOpNode := &ExpressionNode{
 			Operation: deleteImmediateChildOp,
 			Rhs:       createTraversalTree(candidate.Path[0 : len(candidate.Path)-1]),
 		}
@@ -36,20 +36,20 @@ func DeleteChildOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNod
 	return matchingNodes, nil
 }

-func DeleteImmediateChildOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
-	parents, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+func deleteImmediateChildOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
+	parents, err := d.GetMatchingNodes(matchingNodes, expressionNode.Rhs)

 	if err != nil {
 		return nil, err
 	}

-	childPath := pathNode.Operation.Value
+	childPath := expressionNode.Operation.Value

 	log.Debug("childPath to remove %v", childPath)

 	for el := parents.Front(); el != nil; el = el.Next() {
 		parent := el.Value.(*CandidateNode)
-		parentNode := UnwrapDoc(parent.Node)
+		parentNode := unwrapDoc(parent.Node)
 		if parentNode.Kind == yaml.MappingNode {
 			deleteFromMap(parent, childPath)
 		} else if parentNode.Kind == yaml.SequenceNode {
@@ -64,7 +64,7 @@ func DeleteImmediateChildOperator(d *dataTreeNavigator, matchingNodes *list.List

 func deleteFromMap(candidate *CandidateNode, childPath interface{}) {
 	log.Debug("deleteFromMap")
-	node := UnwrapDoc(candidate.Node)
+	node := unwrapDoc(candidate.Node)
 	contents := node.Content
 	newContents := make([]*yaml.Node, 0)

@@ -72,11 +72,7 @@ func deleteFromMap(candidate *CandidateNode, childPath interface{}) {
 		key := contents[index]
 		value := contents[index+1]

-		childCandidate := &CandidateNode{
-			Node:     value,
-			Document: candidate.Document,
-			Path:     candidate.CreateChildPath(key.Value),
-		}
+		childCandidate := candidate.CreateChild(key.Value, value)

 		shouldDelete := key.Value == childPath

@@ -91,7 +87,7 @@ func deleteFromMap(candidate *CandidateNode, childPath interface{}) {

 func deleteFromArray(candidate *CandidateNode, childPath interface{}) {
 	log.Debug("deleteFromArray")
-	node := UnwrapDoc(candidate.Node)
+	node := unwrapDoc(candidate.Node)
 	contents := node.Content
 	newContents := make([]*yaml.Node, 0)

--- a/pkg/yqlib/operator_delete_test.go
+++ b/pkg/yqlib/operator_delete_test.go
@@ -61,6 +61,14 @@ var deleteOperatorScenarios = []expressionScenario{
 			"D0, P[], (doc)::{b: dog}\n",
 		},
 	},
+	{
+		description: "Recursively delete matching keys",
+		document:    `{a: {name: frog, b: {name: blog, age: 12}}}`,
+		expression:  `del(.. | select(has("name")).name)`,
+		expected: []string{
+			"D0, P[], (!!map)::{a: {b: {age: 12}}}\n",
+		},
+	},
 }

 func TestDeleteOperatorScenarios(t *testing.T) {
--- a/pkg/yqlib/operator_document_index.go
+++ b/pkg/yqlib/operator_document_index.go
@@ -7,13 +7,13 @@ import (
 	"gopkg.in/yaml.v3"
 )

-func GetDocumentIndexOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func getDocumentIndexOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	var results = list.New()

 	for el := matchingNodes.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
 		node := &yaml.Node{Kind: yaml.ScalarNode, Value: fmt.Sprintf("%v", candidate.Document), Tag: "!!int"}
-		scalar := &CandidateNode{Node: node, Document: candidate.Document, Path: candidate.Path}
+		scalar := candidate.CreateChild(nil, node)
 		results.PushBack(scalar)
 	}
 	return results, nil
--- a/pkg/yqlib/operator_env.go
+++ b/pkg/yqlib/operator_env.go
@@ -0,0 +1,50 @@
+package yqlib
+
+import (
+	"container/list"
+	"fmt"
+	"os"
+	"strings"
+
+	yaml "gopkg.in/yaml.v3"
+)
+
+type envOpPreferences struct {
+	StringValue bool
+}
+
+func envOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
+	envName := expressionNode.Operation.CandidateNode.Node.Value
+	log.Debug("EnvOperator, env name:", envName)
+
+	rawValue := os.Getenv(envName)
+
+	preferences := expressionNode.Operation.Preferences.(*envOpPreferences)
+
+	var node *yaml.Node
+	if preferences.StringValue {
+		node = &yaml.Node{
+			Kind:  yaml.ScalarNode,
+			Tag:   "!!str",
+			Value: rawValue,
+		}
+	} else if rawValue == "" {
+		return nil, fmt.Errorf("Value for env variable '%v' not provided in env()", envName)
+	} else {
+		var dataBucket yaml.Node
+		decoder := yaml.NewDecoder(strings.NewReader(rawValue))
+		errorReading := decoder.Decode(&dataBucket)
+		if errorReading != nil {
+			return nil, errorReading
+		}
+		//first node is a doc
+		node = unwrapDoc(&dataBucket)
+	}
+	log.Debug("ENV tag", node.Tag)
+	log.Debug("ENV value", node.Value)
+	log.Debug("ENV Kind", node.Kind)
+
+	target := &CandidateNode{Node: node}
+
+	return nodeToMap(target), nil
+}
--- a/pkg/yqlib/operator_env_test.go
+++ b/pkg/yqlib/operator_env_test.go
@@ -0,0 +1,72 @@
+package yqlib
+
+import (
+	"testing"
+)
+
+var envOperatorScenarios = []expressionScenario{
+	{
+		description:         "Read string environment variable",
+		environmentVariable: "cat meow",
+		expression:          `.a = env(myenv)`,
+		expected: []string{
+			"D0, P[], ()::a: cat meow\n",
+		},
+	},
+	{
+		description:         "Read boolean environment variable",
+		environmentVariable: "true",
+		expression:          `.a = env(myenv)`,
+		expected: []string{
+			"D0, P[], ()::a: true\n",
+		},
+	},
+	{
+		description:         "Read numeric environment variable",
+		environmentVariable: "12",
+		expression:          `.a = env(myenv)`,
+		expected: []string{
+			"D0, P[], ()::a: 12\n",
+		},
+	},
+	{
+		description:         "Read yaml environment variable",
+		environmentVariable: "{b: fish}",
+		expression:          `.a = env(myenv)`,
+		expected: []string{
+			"D0, P[], ()::a: {b: fish}\n",
+		},
+	},
+	{
+		description:         "Read boolean environment variable as a string",
+		environmentVariable: "true",
+		expression:          `.a = strenv(myenv)`,
+		expected: []string{
+			"D0, P[], ()::a: \"true\"\n",
+		},
+	},
+	{
+		description:         "Read numeric environment variable as a string",
+		environmentVariable: "12",
+		expression:          `.a = strenv(myenv)`,
+		expected: []string{
+			"D0, P[], ()::a: \"12\"\n",
+		},
+	},
+	{
+		description:         "Dynamic key lookup with environment variable",
+		environmentVariable: "cat",
+		document:            `{cat: meow, dog: woof}`,
+		expression:          `.[env(myenv)]`,
+		expected: []string{
+			"D0, P[cat], (!!str)::meow\n",
+		},
+	},
+}
+
+func TestEnvOperatorScenarios(t *testing.T) {
+	for _, tt := range envOperatorScenarios {
+		testScenario(t, &tt)
+	}
+	documentScenarios(t, "Env Variable Operators", envOperatorScenarios)
+}
--- a/pkg/yqlib/operator_equals.go
+++ b/pkg/yqlib/operator_equals.go
@@ -4,18 +4,21 @@ import (
 	"container/list"
 )

-func EqualsOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func equalsOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("-- equalsOperation")
-	return crossFunction(d, matchingNodes, pathNode, isEquals)
+	return crossFunction(d, matchingNodes, expressionNode, isEquals)
 }

 func isEquals(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
 	value := false

-	if lhs.Node.Tag == "!!null" {
-		value = (rhs.Node.Tag == "!!null")
+	lhsNode := unwrapDoc(lhs.Node)
+	rhsNode := unwrapDoc(rhs.Node)
+
+	if lhsNode.Tag == "!!null" {
+		value = (rhsNode.Tag == "!!null")
 	} else {
-		value = Match(lhs.Node.Value, rhs.Node.Value)
+		value = matchKey(lhsNode.Value, rhsNode.Value)
 	}
 	log.Debugf("%v == %v ? %v", NodeToString(lhs), NodeToString(rhs), value)
 	return createBooleanCandidate(lhs, value), nil
--- a/pkg/yqlib/operator_equals_test.go
+++ b/pkg/yqlib/operator_equals_test.go
@@ -5,6 +5,15 @@ import (
 )

 var equalsOperatorScenarios = []expressionScenario{
+	{
+		skipDoc:    true,
+		document:   "cat",
+		document2:  "dog",
+		expression: "select(fi==0) == select(fi==1)",
+		expected: []string{
+			"D0, P[], (!!bool)::false\n",
+		},
+	},
 	{
 		description: "Match string",
 		document:    `[cat,goat,dog]`,
--- a/pkg/yqlib/operator_file.go
+++ b/pkg/yqlib/operator_file.go
@@ -7,7 +7,7 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )

-func GetFilenameOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func getFilenameOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("GetFilename")

 	var results = list.New()
@@ -15,14 +15,14 @@ func GetFilenameOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNod
 	for el := matchingNodes.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
 		node := &yaml.Node{Kind: yaml.ScalarNode, Value: candidate.Filename, Tag: "!!str"}
-		lengthCand := &CandidateNode{Node: node, Document: candidate.Document, Path: candidate.Path}
-		results.PushBack(lengthCand)
+		result := candidate.CreateChild(nil, node)
+		results.PushBack(result)
 	}

 	return results, nil
 }

-func GetFileIndexOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func getFileIndexOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("GetFileIndex")

 	var results = list.New()
@@ -30,8 +30,8 @@ func GetFileIndexOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNo
 	for el := matchingNodes.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
 		node := &yaml.Node{Kind: yaml.ScalarNode, Value: fmt.Sprintf("%v", candidate.FileIndex), Tag: "!!int"}
-		lengthCand := &CandidateNode{Node: node, Document: candidate.Document, Path: candidate.Path}
-		results.PushBack(lengthCand)
+		result := candidate.CreateChild(nil, node)
+		results.PushBack(result)
 	}

 	return results, nil
--- a/pkg/yqlib/operator_file_test.go
+++ b/pkg/yqlib/operator_file_test.go
@@ -29,6 +29,14 @@ var fileOperatorScenarios = []expressionScenario{
 			"D0, P[], (!!int)::0\n",
 		},
 	},
+	{
+		skipDoc:    true,
+		document:   "a: cat\nb: dog",
+		expression: `.. lineComment |= filename`,
+		expected: []string{
+			"D0, P[], (!!map)::a: cat # sample.yml\nb: dog # sample.yml\n",
+		},
+	},
 }

 func TestFileOperatorsScenarios(t *testing.T) {
--- a/pkg/yqlib/operator_has.go
+++ b/pkg/yqlib/operator_has.go
@@ -7,12 +7,12 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )

-func HasOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func hasOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {

 	log.Debugf("-- hasOperation")
 	var results = list.New()

-	rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+	rhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Rhs)
 	wanted := rhs.Front().Value.(*CandidateNode).Node
 	wantedKey := wanted.Value

@@ -24,8 +24,9 @@ func HasOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathT
 		candidate := el.Value.(*CandidateNode)

 		// grab the first value
-		var contents = candidate.Node.Content
-		switch candidate.Node.Kind {
+		candidateNode := unwrapDoc(candidate.Node)
+		var contents = candidateNode.Content
+		switch candidateNode.Kind {
 		case yaml.MappingNode:
 			candidateHasKey := false
 			for index := 0; index < len(contents) && !candidateHasKey; index = index + 2 {
--- a/pkg/yqlib/operator_has_test.go
+++ b/pkg/yqlib/operator_has_test.go
@@ -5,6 +5,14 @@ import (
 )

 var hasOperatorScenarios = []expressionScenario{
+	{
+		skipDoc:    true,
+		document:   `a: hello`,
+		expression: `has("a")`,
+		expected: []string{
+			"D0, P[], (!!bool)::true\n",
+		},
+	},
 	{
 		description: "Has map key",
 		document: `- a: "yes"
--- a/pkg/yqlib/operator_length.go
+++ b/pkg/yqlib/operator_length.go
@@ -7,13 +7,13 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )

-func LengthOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func lengthOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("-- lengthOperation")
 	var results = list.New()

 	for el := matchMap.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
-		targetNode := UnwrapDoc(candidate.Node)
+		targetNode := unwrapDoc(candidate.Node)
 		var length int
 		switch targetNode.Kind {
 		case yaml.ScalarNode:
@@ -27,8 +27,8 @@ func LengthOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *PathTre
 		}

 		node := &yaml.Node{Kind: yaml.ScalarNode, Value: fmt.Sprintf("%v", length), Tag: "!!int"}
-		lengthCand := &CandidateNode{Node: node, Document: candidate.Document, Path: candidate.Path}
-		results.PushBack(lengthCand)
+		result := candidate.CreateChild(nil, node)
+		results.PushBack(result)
 	}

 	return results, nil
--- a/pkg/yqlib/operator_multiply.go
+++ b/pkg/yqlib/operator_multiply.go
@@ -8,16 +8,16 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )

-type CrossFunctionCalculation func(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error)
+type crossFunctionCalculation func(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error)

-func crossFunction(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode, calculation CrossFunctionCalculation) (*list.List, error) {
-	lhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Lhs)
+func crossFunction(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode, calculation crossFunctionCalculation) (*list.List, error) {
+	lhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Lhs)
 	if err != nil {
 		return nil, err
 	}
 	log.Debugf("crossFunction LHS len: %v", lhs.Len())

-	rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+	rhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Rhs)

 	if err != nil {
 		return nil, err
@@ -43,19 +43,19 @@ func crossFunction(d *dataTreeNavigator, matchingNodes *list.List, pathNode *Pat
 	return results, nil
 }

-type MultiplyPreferences struct {
+type multiplyPreferences struct {
 	AppendArrays bool
 }

-func MultiplyOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func multiplyOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("-- MultiplyOperator")
-	return crossFunction(d, matchingNodes, pathNode, multiply(pathNode.Operation.Preferences.(*MultiplyPreferences)))
+	return crossFunction(d, matchingNodes, expressionNode, multiply(expressionNode.Operation.Preferences.(*multiplyPreferences)))
 }

-func multiply(preferences *MultiplyPreferences) func(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
+func multiply(preferences *multiplyPreferences) func(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
 	return func(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
-		lhs.Node = UnwrapDoc(lhs.Node)
-		rhs.Node = UnwrapDoc(rhs.Node)
+		lhs.Node = unwrapDoc(lhs.Node)
+		rhs.Node = unwrapDoc(rhs.Node)
 		log.Debugf("Multipling LHS: %v", lhs.Node.Tag)
 		log.Debugf("-          RHS: %v", rhs.Node.Tag)

@@ -64,12 +64,7 @@ func multiply(preferences *MultiplyPreferences) func(d *dataTreeNavigator, lhs *
 		if lhs.Node.Kind == yaml.MappingNode && rhs.Node.Kind == yaml.MappingNode ||
 			(lhs.Node.Kind == yaml.SequenceNode && rhs.Node.Kind == yaml.SequenceNode) {

-			var newBlank = &CandidateNode{
-				Path:     lhs.Path,
-				Document: lhs.Document,
-				Filename: lhs.Filename,
-				Node:     &yaml.Node{},
-			}
+			var newBlank = lhs.CreateChild(nil, &yaml.Node{})
 			var newThing, err = mergeObjects(d, newBlank, lhs, false)
 			if err != nil {
 				return nil, err
@@ -85,8 +80,8 @@ func mergeObjects(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode,
 	var results = list.New()

 	// shouldn't recurse arrays if appending
-	prefs := &RecursiveDescentPreferences{RecurseArray: !shouldAppendArrays,
-		TraversePreferences: &TraversePreferences{FollowAlias: false}}
+	prefs := &recursiveDescentPreferences{RecurseArray: !shouldAppendArrays,
+		TraversePreferences: &traversePreferences{FollowAlias: false}}
 	err := recursiveDecent(d, results, nodeToMap(rhs), prefs)
 	if err != nil {
 		return nil, err
@@ -112,16 +107,16 @@ func applyAssignment(d *dataTreeNavigator, pathIndexToStartFrom int, lhs *Candid

 	lhsPath := rhs.Path[pathIndexToStartFrom:]

-	assignmentOp := &Operation{OperationType: AssignAttributes}
+	assignmentOp := &Operation{OperationType: assignAttributesOpType}
 	if rhs.Node.Kind == yaml.ScalarNode || rhs.Node.Kind == yaml.AliasNode {
-		assignmentOp.OperationType = Assign
+		assignmentOp.OperationType = assignOpType
 		assignmentOp.UpdateAssign = false
 	} else if shouldAppendArrays && rhs.Node.Kind == yaml.SequenceNode {
-		assignmentOp.OperationType = AddAssign
+		assignmentOp.OperationType = addAssignOpType
 	}
-	rhsOp := &Operation{OperationType: ValueOp, CandidateNode: rhs}
+	rhsOp := &Operation{OperationType: valueOpType, CandidateNode: rhs}

-	assignmentOpNode := &PathTreeNode{Operation: assignmentOp, Lhs: createTraversalTree(lhsPath), Rhs: &PathTreeNode{Operation: rhsOp}}
+	assignmentOpNode := &ExpressionNode{Operation: assignmentOp, Lhs: createTraversalTree(lhsPath), Rhs: &ExpressionNode{Operation: rhsOp}}

 	_, err := d.GetMatchingNodes(nodeToMap(lhs), assignmentOpNode)

--- a/pkg/yqlib/operator_multiply_test.go
+++ b/pkg/yqlib/operator_multiply_test.go
@@ -132,11 +132,11 @@ b:
 		},
 	},
 	{
-		description: "Merge does not copy anchor names",
+		description: "Merge copies anchor names",
 		document:    `{a: {c: &cat frog}, b: {f: *cat}, c: {g: thongs}}`,
 		expression:  `.c * .a`,
 		expected: []string{
-			"D0, P[c], (!!map)::{g: thongs, c: frog}\n",
+			"D0, P[c], (!!map)::{g: thongs, c: &cat frog}\n",
 		},
 	},
 	{
--- a/pkg/yqlib/operator_path.go
+++ b/pkg/yqlib/operator_path.go
@@ -16,7 +16,7 @@ func createPathNodeFor(pathElement interface{}) *yaml.Node {
 	}
 }

-func GetPathOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func getPathOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("GetPath")

 	var results = list.New()
@@ -31,8 +31,8 @@ func GetPathOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *P
 			content[pathIndex] = createPathNodeFor(path)
 		}
 		node.Content = content
-		lengthCand := &CandidateNode{Node: node, Document: candidate.Document, Path: candidate.Path}
-		results.PushBack(lengthCand)
+		result := candidate.CreateChild(nil, node)
+		results.PushBack(result)
 	}

 	return results, nil
--- a/pkg/yqlib/operator_pipe.go
+++ b/pkg/yqlib/operator_pipe.go
@@ -2,10 +2,10 @@ package yqlib

 import "container/list"

-func PipeOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
-	lhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Lhs)
+func pipeOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
+	lhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Lhs)
 	if err != nil {
 		return nil, err
 	}
-	return d.GetMatchingNodes(lhs, pathNode.Rhs)
+	return d.GetMatchingNodes(lhs, expressionNode.Rhs)
 }
--- a/pkg/yqlib/operator_recursive_descent.go
+++ b/pkg/yqlib/operator_recursive_descent.go
@@ -6,15 +6,15 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )

-type RecursiveDescentPreferences struct {
-	TraversePreferences *TraversePreferences
+type recursiveDescentPreferences struct {
+	TraversePreferences *traversePreferences
 	RecurseArray        bool
 }

-func RecursiveDescentOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func recursiveDescentOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	var results = list.New()

-	preferences := pathNode.Operation.Preferences.(*RecursiveDescentPreferences)
+	preferences := expressionNode.Operation.Preferences.(*recursiveDescentPreferences)
 	err := recursiveDecent(d, results, matchMap, preferences)
 	if err != nil {
 		return nil, err
@@ -23,11 +23,11 @@ func RecursiveDescentOperator(d *dataTreeNavigator, matchMap *list.List, pathNod
 	return results, nil
 }

-func recursiveDecent(d *dataTreeNavigator, results *list.List, matchMap *list.List, preferences *RecursiveDescentPreferences) error {
+func recursiveDecent(d *dataTreeNavigator, results *list.List, matchMap *list.List, preferences *recursiveDescentPreferences) error {
 	for el := matchMap.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)

-		candidate.Node = UnwrapDoc(candidate.Node)
+		candidate.Node = unwrapDoc(candidate.Node)

 		log.Debugf("Recursive Decent, added %v", NodeToString(candidate))
 		results.PushBack(candidate)
@@ -35,7 +35,7 @@ func recursiveDecent(d *dataTreeNavigator, results *list.List, matchMap *list.Li
 		if candidate.Node.Kind != yaml.AliasNode && len(candidate.Node.Content) > 0 &&
 			(preferences.RecurseArray || candidate.Node.Kind != yaml.SequenceNode) {

-			children, err := Splat(d, nodeToMap(candidate), preferences.TraversePreferences)
+			children, err := splat(d, nodeToMap(candidate), preferences.TraversePreferences)

 			if err != nil {
 				return err
--- a/pkg/yqlib/operator_recursive_descent_test.go
+++ b/pkg/yqlib/operator_recursive_descent_test.go
@@ -62,6 +62,24 @@ var recursiveDescentOperatorScenarios = []expressionScenario{
 			"D0, P[a], (!!str)::frog\n",
 		},
 	},
+	{
+		description:    "Recursively find nodes with keys",
+		subdescription: "Note that this example has wrapped the expression in `[]` to show that there are two matches returned. You do not have to wrap in `[]` in your path expression.",
+		document:       `{a: {name: frog, b: {name: blog, age: 12}}}`,
+		expression:     `[.. | select(has("name"))]`,
+		expected: []string{
+			"D0, P[], (!!seq)::- {name: frog, b: {name: blog, age: 12}}\n- {name: blog, age: 12}\n",
+		},
+	},
+	{
+		description: "Recursively find nodes with values",
+		document:    `{a: {nameA: frog, b: {nameB: frog, age: 12}}}`,
+		expression:  `.. | select(. == "frog")`,
+		expected: []string{
+			"D0, P[a nameA], (!!str)::frog\n",
+			"D0, P[a b nameB], (!!str)::frog\n",
+		},
+	},
 	{
 		description:    "Recurse map (values and keys)",
 		subdescription: "Note that the map key appears in the results",
@@ -147,7 +165,7 @@ var recursiveDescentOperatorScenarios = []expressionScenario{
 		document:    `{a: &cat {c: frog}, b: *cat}`,
 		expression:  `[..]`,
 		expected: []string{
-			"D0, P[a], (!!seq)::- {a: &cat {c: frog}, b: *cat}\n- &cat {c: frog}\n- frog\n- *cat\n",
+			"D0, P[], (!!seq)::- {a: &cat {c: frog}, b: *cat}\n- &cat {c: frog}\n- frog\n- *cat\n",
 		},
 	},
 	{
@@ -169,7 +187,7 @@ var recursiveDescentOperatorScenarios = []expressionScenario{
 		document:    mergeDocSample,
 		expression:  `.foobar | [..]`,
 		expected: []string{
-			"D0, P[foobar], (!!seq)::- c: foobar_c\n  !!merge <<: *foo\n  thing: foobar_thing\n- foobar_c\n- *foo\n- foobar_thing\n",
+			"D0, P[], (!!seq)::- c: foobar_c\n  !!merge <<: *foo\n  thing: foobar_thing\n- foobar_c\n- *foo\n- foobar_thing\n",
 		},
 	},
 	{
@@ -177,7 +195,7 @@ var recursiveDescentOperatorScenarios = []expressionScenario{
 		document:   mergeDocSample,
 		expression: `.foobar | [...]`,
 		expected: []string{
-			"D0, P[foobar], (!!seq)::- c: foobar_c\n  !!merge <<: *foo\n  thing: foobar_thing\n- c\n- foobar_c\n- !!merge <<\n- *foo\n- thing\n- foobar_thing\n",
+			"D0, P[], (!!seq)::- c: foobar_c\n  !!merge <<: *foo\n  thing: foobar_thing\n- c\n- foobar_c\n- !!merge <<\n- *foo\n- thing\n- foobar_thing\n",
 		},
 	},
 	{
@@ -215,5 +233,5 @@ func TestRecursiveDescentOperatorScenarios(t *testing.T) {
 	for _, tt := range recursiveDescentOperatorScenarios {
 		testScenario(t, &tt)
 	}
-	documentScenarios(t, "Recursive Descent", recursiveDescentOperatorScenarios)
+	documentScenarios(t, "Recursive Descent (Glob)", recursiveDescentOperatorScenarios)
 }
--- a/pkg/yqlib/operator_select.go
+++ b/pkg/yqlib/operator_select.go
@@ -4,7 +4,7 @@ import (
 	"container/list"
 )

-func SelectOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func selectOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {

 	log.Debugf("-- selectOperation")
 	var results = list.New()
@@ -12,7 +12,7 @@ func SelectOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *Pa
 	for el := matchingNodes.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)

-		rhs, err := d.GetMatchingNodes(nodeToMap(candidate), pathNode.Rhs)
+		rhs, err := d.GetMatchingNodes(nodeToMap(candidate), expressionNode.Rhs)

 		if err != nil {
 			return nil, err
--- a/pkg/yqlib/operator_self.go
+++ b/pkg/yqlib/operator_self.go
@@ -2,6 +2,6 @@ package yqlib

 import "container/list"

-func SelfOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func selfOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	return matchMap, nil
 }
--- a/pkg/yqlib/operator_sort_keys.go
+++ b/pkg/yqlib/operator_sort_keys.go
@@ -7,17 +7,17 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )

-func SortKeysOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func sortKeysOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {

 	for el := matchingNodes.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
-		rhs, err := d.GetMatchingNodes(nodeToMap(candidate), pathNode.Rhs)
+		rhs, err := d.GetMatchingNodes(nodeToMap(candidate), expressionNode.Rhs)
 		if err != nil {
 			return nil, err
 		}

 		for childEl := rhs.Front(); childEl != nil; childEl = childEl.Next() {
-			node := UnwrapDoc(childEl.Value.(*CandidateNode).Node)
+			node := unwrapDoc(childEl.Value.(*CandidateNode).Node)
 			if node.Kind == yaml.MappingNode {
 				sortKeys(node)
 			}
--- a/pkg/yqlib/operator_style.go
+++ b/pkg/yqlib/operator_style.go
@@ -26,12 +26,12 @@ func parseStyle(customStyle string) (yaml.Style, error) {
 	return 0, nil
 }

-func AssignStyleOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func assignStyleOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {

 	log.Debugf("AssignStyleOperator: %v")
 	var style yaml.Style
-	if !pathNode.Operation.UpdateAssign {
-		rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+	if !expressionNode.Operation.UpdateAssign {
+		rhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Rhs)
 		if err != nil {
 			return nil, err
 		}
@@ -44,7 +44,7 @@ func AssignStyleOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNod
 		}
 	}

-	lhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Lhs)
+	lhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Lhs)

 	if err != nil {
 		return nil, err
@@ -53,8 +53,8 @@ func AssignStyleOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNod
 	for el := lhs.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
 		log.Debugf("Setting style of : %v", candidate.GetKey())
-		if pathNode.Operation.UpdateAssign {
-			rhs, err := d.GetMatchingNodes(nodeToMap(candidate), pathNode.Rhs)
+		if expressionNode.Operation.UpdateAssign {
+			rhs, err := d.GetMatchingNodes(nodeToMap(candidate), expressionNode.Rhs)
 			if err != nil {
 				return nil, err
 			}
@@ -73,7 +73,7 @@ func AssignStyleOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNod
 	return matchingNodes, nil
 }

-func GetStyleOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func getStyleOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("GetStyleOperator")

 	var results = list.New()
@@ -100,8 +100,8 @@ func GetStyleOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *
 			style = "<unknown>"
 		}
 		node := &yaml.Node{Kind: yaml.ScalarNode, Value: style, Tag: "!!str"}
-		lengthCand := &CandidateNode{Node: node, Document: candidate.Document, Path: candidate.Path}
-		results.PushBack(lengthCand)
+		result := candidate.CreateChild(nil, node)
+		results.PushBack(result)
 	}

 	return results, nil
--- a/pkg/yqlib/operator_tag.go
+++ b/pkg/yqlib/operator_tag.go
@@ -6,13 +6,13 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )

-func AssignTagOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func assignTagOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {

 	log.Debugf("AssignTagOperator: %v")
 	tag := ""

-	if !pathNode.Operation.UpdateAssign {
-		rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+	if !expressionNode.Operation.UpdateAssign {
+		rhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Rhs)
 		if err != nil {
 			return nil, err
 		}
@@ -22,7 +22,7 @@ func AssignTagOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode
 		}
 	}

-	lhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Lhs)
+	lhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Lhs)

 	if err != nil {
 		return nil, err
@@ -31,8 +31,8 @@ func AssignTagOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode
 	for el := lhs.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
 		log.Debugf("Setting tag of : %v", candidate.GetKey())
-		if pathNode.Operation.UpdateAssign {
-			rhs, err := d.GetMatchingNodes(nodeToMap(candidate), pathNode.Rhs)
+		if expressionNode.Operation.UpdateAssign {
+			rhs, err := d.GetMatchingNodes(nodeToMap(candidate), expressionNode.Rhs)
 			if err != nil {
 				return nil, err
 			}
@@ -41,22 +41,22 @@ func AssignTagOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode
 				tag = rhs.Front().Value.(*CandidateNode).Node.Value
 			}
 		}
-		candidate.Node.Tag = tag
+		unwrapDoc(candidate.Node).Tag = tag
 	}

 	return matchingNodes, nil
 }

-func GetTagOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func getTagOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("GetTagOperator")

 	var results = list.New()

 	for el := matchingNodes.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
-		node := &yaml.Node{Kind: yaml.ScalarNode, Value: UnwrapDoc(candidate.Node).Tag, Tag: "!!str"}
-		lengthCand := &CandidateNode{Node: node, Document: candidate.Document, Path: candidate.Path}
-		results.PushBack(lengthCand)
+		node := &yaml.Node{Kind: yaml.ScalarNode, Value: unwrapDoc(candidate.Node).Tag, Tag: "!!str"}
+		result := candidate.CreateChild(nil, node)
+		results.PushBack(result)
 	}

 	return results, nil
--- a/pkg/yqlib/operator_tag_test.go
+++ b/pkg/yqlib/operator_tag_test.go
@@ -26,6 +26,14 @@ var tagOperatorScenarios = []expressionScenario{
 			"D0, P[], (!!str)::'!!map'\n",
 		},
 	},
+	{
+		skipDoc:    true,
+		document:   `32`,
+		expression: `. tag= "!!str"`,
+		expected: []string{
+			"D0, P[], (doc)::\"32\"\n",
+		},
+	},
 	{
 		description: "Set custom tag",
 		document:    `{a: str}`,
--- a/pkg/yqlib/operator_traverse_path.go
+++ b/pkg/yqlib/operator_traverse_path.go
@@ -9,21 +9,21 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )

-type TraversePreferences struct {
+type traversePreferences struct {
 	FollowAlias    bool
 	IncludeMapKeys bool
 }

-func Splat(d *dataTreeNavigator, matches *list.List, prefs *TraversePreferences) (*list.List, error) {
+func splat(d *dataTreeNavigator, matches *list.List, prefs *traversePreferences) (*list.List, error) {
 	return traverseNodesWithArrayIndices(matches, make([]*yaml.Node, 0), prefs)
 }

-func TraversePathOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func traversePathOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("-- Traversing")
 	var matchingNodeMap = list.New()

 	for el := matchMap.Front(); el != nil; el = el.Next() {
-		newNodes, err := traverse(d, el.Value.(*CandidateNode), pathNode.Operation)
+		newNodes, err := traverse(d, el.Value.(*CandidateNode), expressionNode.Operation)
 		if err != nil {
 			return nil, err
 		}
@@ -54,7 +54,7 @@ func traverse(d *dataTreeNavigator, matchingNode *CandidateNode, operation *Oper
 	switch value.Kind {
 	case yaml.MappingNode:
 		log.Debug("its a map with %v entries", len(value.Content)/2)
-		prefs := &TraversePreferences{FollowAlias: true}
+		prefs := &traversePreferences{FollowAlias: true}
 		return traverseMap(matchingNode, operation.StringValue, prefs, false)

 	case yaml.SequenceNode:
@@ -67,30 +67,27 @@ func traverse(d *dataTreeNavigator, matchingNode *CandidateNode, operation *Oper
 		return traverse(d, matchingNode, operation)
 	case yaml.DocumentNode:
 		log.Debug("digging into doc node")
-		return traverse(d, &CandidateNode{
-			Node:      matchingNode.Node.Content[0],
-			Filename:  matchingNode.Filename,
-			FileIndex: matchingNode.FileIndex,
-			Document:  matchingNode.Document}, operation)
+
+		return traverse(d, matchingNode.CreateChild(nil, matchingNode.Node.Content[0]), operation)
 	default:
 		return list.New(), nil
 	}
 }

-func TraverseArrayOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func traverseArrayOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	// rhs is a collect expression that will yield indexes to retreive of the arrays

-	rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+	rhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Rhs)
 	if err != nil {
 		return nil, err
 	}

 	var indicesToTraverse = rhs.Front().Value.(*CandidateNode).Node.Content
-	prefs := &TraversePreferences{FollowAlias: true}
+	prefs := &traversePreferences{FollowAlias: true}
 	return traverseNodesWithArrayIndices(matchingNodes, indicesToTraverse, prefs)
 }

-func traverseNodesWithArrayIndices(matchingNodes *list.List, indicesToTraverse []*yaml.Node, prefs *TraversePreferences) (*list.List, error) {
+func traverseNodesWithArrayIndices(matchingNodes *list.List, indicesToTraverse []*yaml.Node, prefs *traversePreferences) (*list.List, error) {
 	var matchingNodeMap = list.New()
 	for el := matchingNodes.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
@@ -104,7 +101,7 @@ func traverseNodesWithArrayIndices(matchingNodes *list.List, indicesToTraverse [
 	return matchingNodeMap, nil
 }

-func traverseArrayIndices(matchingNode *CandidateNode, indicesToTraverse []*yaml.Node, prefs *TraversePreferences) (*list.List, error) { // call this if doc / alias like the other traverse
+func traverseArrayIndices(matchingNode *CandidateNode, indicesToTraverse []*yaml.Node, prefs *traversePreferences) (*list.List, error) { // call this if doc / alias like the other traverse
 	node := matchingNode.Node
 	if node.Tag == "!!null" {
 		log.Debugf("OperatorArrayTraverse got a null - turning it into an empty array")
@@ -121,17 +118,13 @@ func traverseArrayIndices(matchingNode *CandidateNode, indicesToTraverse []*yaml
 	} else if node.Kind == yaml.MappingNode {
 		return traverseMapWithIndices(matchingNode, indicesToTraverse, prefs)
 	} else if node.Kind == yaml.DocumentNode {
-		return traverseArrayIndices(&CandidateNode{
-			Node:      matchingNode.Node.Content[0],
-			Filename:  matchingNode.Filename,
-			FileIndex: matchingNode.FileIndex,
-			Document:  matchingNode.Document}, indicesToTraverse, prefs)
+		return traverseArrayIndices(matchingNode.CreateChild(nil, matchingNode.Node.Content[0]), indicesToTraverse, prefs)
 	}
 	log.Debugf("OperatorArrayTraverse skipping %v as its a %v", matchingNode, node.Tag)
 	return list.New(), nil
 }

-func traverseMapWithIndices(candidate *CandidateNode, indices []*yaml.Node, prefs *TraversePreferences) (*list.List, error) {
+func traverseMapWithIndices(candidate *CandidateNode, indices []*yaml.Node, prefs *traversePreferences) (*list.List, error) {
 	if len(indices) == 0 {
 		return traverseMap(candidate, "", prefs, true)
 	}
@@ -153,17 +146,13 @@ func traverseMapWithIndices(candidate *CandidateNode, indices []*yaml.Node, pref
 func traverseArrayWithIndices(candidate *CandidateNode, indices []*yaml.Node) (*list.List, error) {
 	log.Debug("traverseArrayWithIndices")
 	var newMatches = list.New()
-	node := UnwrapDoc(candidate.Node)
+	node := unwrapDoc(candidate.Node)
 	if len(indices) == 0 {
 		log.Debug("splatting")
 		var index int64
 		for index = 0; index < int64(len(node.Content)); index = index + 1 {

-			newMatches.PushBack(&CandidateNode{
-				Document: candidate.Document,
-				Path:     candidate.CreateChildPath(index),
-				Node:     node.Content[index],
-			})
+			newMatches.PushBack(candidate.CreateChild(index, node.Content[index]))
 		}
 		return newMatches, nil

@@ -190,20 +179,16 @@ func traverseArrayWithIndices(candidate *CandidateNode, indices []*yaml.Node) (*
 			return nil, fmt.Errorf("Index [%v] out of range, array size is %v", index, contentLength)
 		}

-		newMatches.PushBack(&CandidateNode{
-			Node:     node.Content[indexToUse],
-			Document: candidate.Document,
-			Path:     candidate.CreateChildPath(index),
-		})
+		newMatches.PushBack(candidate.CreateChild(index, node.Content[indexToUse]))
 	}
 	return newMatches, nil
 }

 func keyMatches(key *yaml.Node, wantedKey string) bool {
-	return Match(key.Value, wantedKey)
+	return matchKey(key.Value, wantedKey)
 }

-func traverseMap(matchingNode *CandidateNode, key string, prefs *TraversePreferences, splat bool) (*list.List, error) {
+func traverseMap(matchingNode *CandidateNode, key string, prefs *traversePreferences, splat bool) (*list.List, error) {
 	var newMatches = orderedmap.NewOrderedMap()
 	err := doTraverseMap(newMatches, matchingNode, key, prefs, splat)

@@ -216,13 +201,8 @@ func traverseMap(matchingNode *CandidateNode, key string, prefs *TraversePrefere
 		valueNode := &yaml.Node{Tag: "!!null", Kind: yaml.ScalarNode, Value: "null"}
 		node := matchingNode.Node
 		node.Content = append(node.Content, &yaml.Node{Kind: yaml.ScalarNode, Value: key}, valueNode)
-		candidateNode := &CandidateNode{
-			Node:     valueNode,
-			Path:     append(matchingNode.Path, key),
-			Document: matchingNode.Document,
-		}
+		candidateNode := matchingNode.CreateChild(key, valueNode)
 		newMatches.Set(candidateNode.GetKey(), candidateNode)
-
 	}

 	results := list.New()
@@ -234,7 +214,7 @@ func traverseMap(matchingNode *CandidateNode, key string, prefs *TraversePrefere
 	return results, nil
 }

-func doTraverseMap(newMatches *orderedmap.OrderedMap, candidate *CandidateNode, wantedKey string, prefs *TraversePreferences, splat bool) error {
+func doTraverseMap(newMatches *orderedmap.OrderedMap, candidate *CandidateNode, wantedKey string, prefs *traversePreferences, splat bool) error {
 	// value.Content is a concatenated array of key, value,
 	// so keys are in the even indexes, values in odd.
 	// merge aliases are defined first, but we only want to traverse them
@@ -258,18 +238,10 @@ func doTraverseMap(newMatches *orderedmap.OrderedMap, candidate *CandidateNode,
 		} else if splat || keyMatches(key, wantedKey) {
 			log.Debug("MATCHED")
 			if prefs.IncludeMapKeys {
-				candidateNode := &CandidateNode{
-					Node:     key,
-					Path:     candidate.CreateChildPath(key.Value),
-					Document: candidate.Document,
-				}
+				candidateNode := candidate.CreateChild(key.Value, key)
 				newMatches.Set(fmt.Sprintf("keyOf-%v", candidateNode.GetKey()), candidateNode)
 			}
-			candidateNode := &CandidateNode{
-				Node:     value,
-				Path:     candidate.CreateChildPath(key.Value),
-				Document: candidate.Document,
-			}
+			candidateNode := candidate.CreateChild(key.Value, value)
 			newMatches.Set(candidateNode.GetKey(), candidateNode)
 		}
 	}
@@ -277,14 +249,10 @@ func doTraverseMap(newMatches *orderedmap.OrderedMap, candidate *CandidateNode,
 	return nil
 }

-func traverseMergeAnchor(newMatches *orderedmap.OrderedMap, originalCandidate *CandidateNode, value *yaml.Node, wantedKey string, prefs *TraversePreferences, splat bool) error {
+func traverseMergeAnchor(newMatches *orderedmap.OrderedMap, originalCandidate *CandidateNode, value *yaml.Node, wantedKey string, prefs *traversePreferences, splat bool) error {
 	switch value.Kind {
 	case yaml.AliasNode:
-		candidateNode := &CandidateNode{
-			Node:     value.Alias,
-			Path:     originalCandidate.Path,
-			Document: originalCandidate.Document,
-		}
+		candidateNode := originalCandidate.CreateChild(nil, value.Alias)
 		return doTraverseMap(newMatches, candidateNode, wantedKey, prefs, splat)
 	case yaml.SequenceNode:
 		for _, childValue := range value.Content {
--- a/pkg/yqlib/operator_traverse_path_test.go
+++ b/pkg/yqlib/operator_traverse_path_test.go
@@ -54,6 +54,15 @@ var traversePathOperatorScenarios = []expressionScenario{
 			"D0, P[{}], (!!str)::frog\n",
 		},
 	},
+	{
+		description:    "Dynamic keys",
+		subdescription: `Expressions within [] can be used to dynamically lookup / calculate keys`,
+		document:       `{b: apple, apple: crispy yum, banana: soft yum}`,
+		expression:     `.[.b]`,
+		expected: []string{
+			"D0, P[apple], (!!str)::crispy yum\n",
+		},
+	},
 	{
 		description:    "Children don't exist",
 		subdescription: "Nodes are added dynamically while traversing",
--- a/pkg/yqlib/operator_union.go
+++ b/pkg/yqlib/operator_union.go
@@ -2,12 +2,12 @@ package yqlib

 import "container/list"

-func UnionOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
-	lhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Lhs)
+func unionOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
+	lhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Lhs)
 	if err != nil {
 		return nil, err
 	}
-	rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+	rhs, err := d.GetMatchingNodes(matchingNodes, expressionNode.Rhs)
 	if err != nil {
 		return nil, err
 	}
--- a/pkg/yqlib/operator_value.go
+++ b/pkg/yqlib/operator_value.go
@@ -2,7 +2,7 @@ package yqlib

 import "container/list"

-func ValueOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *PathTreeNode) (*list.List, error) {
-	log.Debug("value = %v", pathNode.Operation.CandidateNode.Node.Value)
-	return nodeToMap(pathNode.Operation.CandidateNode), nil
+func valueOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
+	log.Debug("value = %v", expressionNode.Operation.CandidateNode.Node.Value)
+	return nodeToMap(expressionNode.Operation.CandidateNode), nil
 }
--- a/pkg/yqlib/operators.go
+++ b/pkg/yqlib/operators.go
@@ -7,16 +7,16 @@ import (
 	"gopkg.in/yaml.v3"
 )

-type OperatorHandler func(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error)
+type operatorHandler func(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error)

-func UnwrapDoc(node *yaml.Node) *yaml.Node {
+func unwrapDoc(node *yaml.Node) *yaml.Node {
 	if node.Kind == yaml.DocumentNode {
 		return node.Content[0]
 	}
 	return node
 }

-func EmptyOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+func emptyOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	return list.New(), nil
 }

@@ -26,7 +26,7 @@ func createBooleanCandidate(owner *CandidateNode, value bool) *CandidateNode {
 		valString = "false"
 	}
 	node := &yaml.Node{Kind: yaml.ScalarNode, Value: valString, Tag: "!!bool"}
-	return &CandidateNode{Node: node, Document: owner.Document, Path: owner.Path}
+	return owner.CreateChild(nil, node)
 }

 func nodeToMap(candidate *CandidateNode) *list.List {
@@ -35,14 +35,14 @@ func nodeToMap(candidate *CandidateNode) *list.List {
 	return elMap
 }

-func createTraversalTree(path []interface{}) *PathTreeNode {
+func createTraversalTree(path []interface{}) *ExpressionNode {
 	if len(path) == 0 {
-		return &PathTreeNode{Operation: &Operation{OperationType: SelfReference}}
+		return &ExpressionNode{Operation: &Operation{OperationType: selfReferenceOpType}}
 	} else if len(path) == 1 {
-		return &PathTreeNode{Operation: &Operation{OperationType: TraversePath, Value: path[0], StringValue: fmt.Sprintf("%v", path[0])}}
+		return &ExpressionNode{Operation: &Operation{OperationType: traversePathOpType, Value: path[0], StringValue: fmt.Sprintf("%v", path[0])}}
 	}
-	return &PathTreeNode{
-		Operation: &Operation{OperationType: ShortPipe},
+	return &ExpressionNode{
+		Operation: &Operation{OperationType: shortPipeOpType},
 		Lhs:       createTraversalTree(path[0:1]),
 		Rhs:       createTraversalTree(path[1:])}
 }
--- a/pkg/yqlib/operators_test.go
+++ b/pkg/yqlib/operators_test.go
@@ -17,6 +17,7 @@ import (
 type expressionScenario struct {
 	description           string
 	subdescription        string
+	environmentVariable   string
 	document              string
 	document2             string
 	expression            string
@@ -29,7 +30,7 @@ func testScenario(t *testing.T, s *expressionScenario) {
 	var results *list.List
 	var err error

-	node, err := treeCreator.ParsePath(s.expression)
+	node, err := NewExpressionParser().ParseExpression(s.expression)
 	if err != nil {
 		t.Error(fmt.Errorf("Error parsing expression %v of %v: %v", s.expression, s.description, err))
 		return
@@ -61,7 +62,11 @@ func testScenario(t *testing.T, s *expressionScenario) {

 	}

-	results, err = treeNavigator.GetMatchingNodes(inputs, node)
+	if s.environmentVariable != "" {
+		os.Setenv("myenv", s.environmentVariable)
+	}
+
+	results, err = NewDataTreeNavigator().GetMatchingNodes(inputs, node)

 	if err != nil {
 		t.Error(fmt.Errorf("%v: %v", err, s.expression))
@@ -105,7 +110,7 @@ func formatYaml(yaml string, filename string) string {
 	var output bytes.Buffer
 	printer := NewPrinter(bufio.NewWriter(&output), false, true, false, 2, true)

-	node, err := treeCreator.ParsePath(".. style= \"\"")
+	node, err := NewExpressionParser().ParseExpression(".. style= \"\"")
 	if err != nil {
 		panic(err)
 	}
@@ -162,6 +167,14 @@ func documentInput(w *bufio.Writer, s expressionScenario) (string, string) {
 	formattedDoc := ""
 	formattedDoc2 := ""
 	command := "eval"
+
+	envCommand := ""
+
+	if s.environmentVariable != "" {
+		envCommand = fmt.Sprintf("myenv=\"%v\" ", s.environmentVariable)
+		os.Setenv("myenv", s.environmentVariable)
+	}
+
 	if s.document != "" {
 		if s.dontFormatInputForDoc {
 			formattedDoc = s.document + "\n"
@@ -188,14 +201,15 @@ func documentInput(w *bufio.Writer, s expressionScenario) (string, string) {
 		}

 		writeOrPanic(w, "then\n")
+
 		if s.expression != "" {
-			writeOrPanic(w, fmt.Sprintf("```bash\nyq %v '%v' %v\n```\n", command, s.expression, files))
+			writeOrPanic(w, fmt.Sprintf("```bash\n%vyq %v '%v' %v\n```\n", envCommand, command, s.expression, files))
 		} else {
-			writeOrPanic(w, fmt.Sprintf("```bash\nyq %v %v\n```\n", command, files))
+			writeOrPanic(w, fmt.Sprintf("```bash\n%vyq %v %v\n```\n", envCommand, command, files))
 		}
 	} else {
 		writeOrPanic(w, "Running\n")
-		writeOrPanic(w, fmt.Sprintf("```bash\nyq %v --null-input '%v'\n```\n", command, s.expression))
+		writeOrPanic(w, fmt.Sprintf("```bash\n%vyq %v --null-input '%v'\n```\n", envCommand, command, s.expression))
 	}
 	return formattedDoc, formattedDoc2
 }
@@ -205,7 +219,7 @@ func documentOutput(t *testing.T, w *bufio.Writer, s expressionScenario, formatt
 	var err error
 	printer := NewPrinter(bufio.NewWriter(&output), false, true, false, 2, true)

-	node, err := treeCreator.ParsePath(s.expression)
+	node, err := NewExpressionParser().ParseExpression(s.expression)
 	if err != nil {
 		t.Error(fmt.Errorf("Error parsing expression %v of %v: %v", s.expression, s.description, err))
 		return
@@ -238,7 +252,7 @@ func documentOutput(t *testing.T, w *bufio.Writer, s expressionScenario, formatt

 	}

-	results, err := treeNavigator.GetMatchingNodes(inputs, node)
+	results, err := NewDataTreeNavigator().GetMatchingNodes(inputs, node)
 	if err != nil {
 		t.Error(err, s.expression)
 	}
--- a/pkg/yqlib/path_tokeniser.go
+++ b/pkg/yqlib/path_tokeniser.go
@@ -1,383 +0,0 @@
-package yqlib
-
-import (
-	"fmt"
-	"strconv"
-
-	lex "github.com/timtadh/lexmachine"
-	"github.com/timtadh/lexmachine/machines"
-)
-
-func skip(*lex.Scanner, *machines.Match) (interface{}, error) {
-	return nil, nil
-}
-
-type TokenType uint32
-
-const (
-	OperationToken = 1 << iota
-	OpenBracket
-	CloseBracket
-	OpenCollect
-	CloseCollect
-	OpenCollectObject
-	CloseCollectObject
-	TraverseArrayCollect
-)
-
-type Token struct {
-	TokenType            TokenType
-	Operation            *Operation
-	AssignOperation      *Operation // e.g. tag (GetTag) op becomes AssignTag if '=' follows it
-	CheckForPostTraverse bool       // e.g. [1]cat should really be [1].cat
-
-}
-
-func (t *Token) toString() string {
-	if t.TokenType == OperationToken {
-		log.Debug("toString, its an op")
-		return t.Operation.toString()
-	} else if t.TokenType == OpenBracket {
-		return "("
-	} else if t.TokenType == CloseBracket {
-		return ")"
-	} else if t.TokenType == OpenCollect {
-		return "["
-	} else if t.TokenType == CloseCollect {
-		return "]"
-	} else if t.TokenType == OpenCollectObject {
-		return "{"
-	} else if t.TokenType == CloseCollectObject {
-		return "}"
-	} else if t.TokenType == TraverseArrayCollect {
-		return ".["
-
-	} else {
-		return "NFI"
-	}
-}
-
-func pathToken(wrapped bool) lex.Action {
-	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
-		value := string(m.Bytes)
-		value = value[1:]
-		if wrapped {
-			value = unwrap(value)
-		}
-		log.Debug("PathToken %v", value)
-		op := &Operation{OperationType: TraversePath, Value: value, StringValue: value}
-		return &Token{TokenType: OperationToken, Operation: op, CheckForPostTraverse: true}, nil
-	}
-}
-
-func documentToken() lex.Action {
-	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
-		var numberString = string(m.Bytes)
-		numberString = numberString[1:]
-		var number, errParsingInt = strconv.ParseInt(numberString, 10, 64) // nolint
-		if errParsingInt != nil {
-			return nil, errParsingInt
-		}
-		log.Debug("documentToken %v", string(m.Bytes))
-		op := &Operation{OperationType: DocumentFilter, Value: number, StringValue: numberString}
-		return &Token{TokenType: OperationToken, Operation: op, CheckForPostTraverse: true}, nil
-	}
-}
-
-func opToken(op *OperationType) lex.Action {
-	return opTokenWithPrefs(op, nil, nil)
-}
-
-func opAssignableToken(opType *OperationType, assignOpType *OperationType) lex.Action {
-	return opTokenWithPrefs(opType, assignOpType, nil)
-}
-
-func assignOpToken(updateAssign bool) lex.Action {
-	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
-		log.Debug("assignOpToken %v", string(m.Bytes))
-		value := string(m.Bytes)
-		op := &Operation{OperationType: Assign, Value: Assign.Type, StringValue: value, UpdateAssign: updateAssign}
-		return &Token{TokenType: OperationToken, Operation: op}, nil
-	}
-}
-
-func opTokenWithPrefs(op *OperationType, assignOpType *OperationType, preferences interface{}) lex.Action {
-	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
-		log.Debug("opTokenWithPrefs %v", string(m.Bytes))
-		value := string(m.Bytes)
-		op := &Operation{OperationType: op, Value: op.Type, StringValue: value, Preferences: preferences}
-		var assign *Operation
-		if assignOpType != nil {
-			assign = &Operation{OperationType: assignOpType, Value: assignOpType.Type, StringValue: value, Preferences: preferences}
-		}
-		return &Token{TokenType: OperationToken, Operation: op, AssignOperation: assign}, nil
-	}
-}
-
-func assignAllCommentsOp(updateAssign bool) lex.Action {
-	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
-		log.Debug("assignAllCommentsOp %v", string(m.Bytes))
-		value := string(m.Bytes)
-		op := &Operation{
-			OperationType: AssignComment,
-			Value:         AssignComment.Type,
-			StringValue:   value,
-			UpdateAssign:  updateAssign,
-			Preferences:   &CommentOpPreferences{LineComment: true, HeadComment: true, FootComment: true},
-		}
-		return &Token{TokenType: OperationToken, Operation: op}, nil
-	}
-}
-
-func literalToken(pType TokenType, checkForPost bool) lex.Action {
-	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
-		return &Token{TokenType: pType, CheckForPostTraverse: checkForPost}, nil
-	}
-}
-
-func unwrap(value string) string {
-	return value[1 : len(value)-1]
-}
-
-func numberValue() lex.Action {
-	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
-		var numberString = string(m.Bytes)
-		var number, errParsingInt = strconv.ParseInt(numberString, 10, 64) // nolint
-		if errParsingInt != nil {
-			return nil, errParsingInt
-		}
-
-		return &Token{TokenType: OperationToken, Operation: CreateValueOperation(number, numberString)}, nil
-	}
-}
-
-func floatValue() lex.Action {
-	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
-		var numberString = string(m.Bytes)
-		var number, errParsingInt = strconv.ParseFloat(numberString, 64) // nolint
-		if errParsingInt != nil {
-			return nil, errParsingInt
-		}
-		return &Token{TokenType: OperationToken, Operation: CreateValueOperation(number, numberString)}, nil
-	}
-}
-
-func booleanValue(val bool) lex.Action {
-	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
-		return &Token{TokenType: OperationToken, Operation: CreateValueOperation(val, string(m.Bytes))}, nil
-	}
-}
-
-func stringValue(wrapped bool) lex.Action {
-	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
-		value := string(m.Bytes)
-		if wrapped {
-			value = unwrap(value)
-		}
-		return &Token{TokenType: OperationToken, Operation: CreateValueOperation(value, value)}, nil
-	}
-}
-
-func nullValue() lex.Action {
-	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
-		return &Token{TokenType: OperationToken, Operation: CreateValueOperation(nil, string(m.Bytes))}, nil
-	}
-}
-
-func selfToken() lex.Action {
-	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
-		op := &Operation{OperationType: SelfReference}
-		return &Token{TokenType: OperationToken, Operation: op}, nil
-	}
-}
-
-func initLexer() (*lex.Lexer, error) {
-	lexer := lex.NewLexer()
-	lexer.Add([]byte(`\(`), literalToken(OpenBracket, false))
-	lexer.Add([]byte(`\)`), literalToken(CloseBracket, true))
-
-	lexer.Add([]byte(`\.\[`), literalToken(TraverseArrayCollect, false))
-	lexer.Add([]byte(`\.\.`), opTokenWithPrefs(RecursiveDescent, nil, &RecursiveDescentPreferences{RecurseArray: true,
-		TraversePreferences: &TraversePreferences{FollowAlias: false, IncludeMapKeys: false}}))
-
-	lexer.Add([]byte(`\.\.\.`), opTokenWithPrefs(RecursiveDescent, nil, &RecursiveDescentPreferences{RecurseArray: true,
-		TraversePreferences: &TraversePreferences{FollowAlias: false, IncludeMapKeys: true}}))
-
-	lexer.Add([]byte(`,`), opToken(Union))
-	lexer.Add([]byte(`:\s*`), opToken(CreateMap))
-	lexer.Add([]byte(`length`), opToken(Length))
-	lexer.Add([]byte(`sortKeys`), opToken(SortKeys))
-	lexer.Add([]byte(`select`), opToken(Select))
-	lexer.Add([]byte(`has`), opToken(Has))
-	lexer.Add([]byte(`explode`), opToken(Explode))
-	lexer.Add([]byte(`or`), opToken(Or))
-	lexer.Add([]byte(`and`), opToken(And))
-	lexer.Add([]byte(`not`), opToken(Not))
-	lexer.Add([]byte(`\/\/`), opToken(Alternative))
-
-	lexer.Add([]byte(`documentIndex`), opToken(GetDocumentIndex))
-	lexer.Add([]byte(`di`), opToken(GetDocumentIndex))
-
-	lexer.Add([]byte(`style`), opAssignableToken(GetStyle, AssignStyle))
-
-	lexer.Add([]byte(`tag`), opAssignableToken(GetTag, AssignTag))
-	lexer.Add([]byte(`anchor`), opAssignableToken(GetAnchor, AssignAnchor))
-	lexer.Add([]byte(`alias`), opAssignableToken(GetAlias, AssignAlias))
-	lexer.Add([]byte(`filename`), opToken(GetFilename))
-	lexer.Add([]byte(`fileIndex`), opToken(GetFileIndex))
-	lexer.Add([]byte(`fi`), opToken(GetFileIndex))
-	lexer.Add([]byte(`path`), opToken(GetPath))
-
-	lexer.Add([]byte(`lineComment`), opTokenWithPrefs(GetComment, AssignComment, &CommentOpPreferences{LineComment: true}))
-
-	lexer.Add([]byte(`headComment`), opTokenWithPrefs(GetComment, AssignComment, &CommentOpPreferences{HeadComment: true}))
-
-	lexer.Add([]byte(`footComment`), opTokenWithPrefs(GetComment, AssignComment, &CommentOpPreferences{FootComment: true}))
-
-	lexer.Add([]byte(`comments\s*=`), assignAllCommentsOp(false))
-	lexer.Add([]byte(`comments\s*\|=`), assignAllCommentsOp(true))
-
-	lexer.Add([]byte(`collect`), opToken(Collect))
-
-	lexer.Add([]byte(`\s*==\s*`), opToken(Equals))
-	lexer.Add([]byte(`\s*=\s*`), assignOpToken(false))
-
-	lexer.Add([]byte(`del`), opToken(DeleteChild))
-
-	lexer.Add([]byte(`\s*\|=\s*`), assignOpToken(true))
-
-	lexer.Add([]byte("( |\t|\n|\r)+"), skip)
-
-	lexer.Add([]byte(`d[0-9]+`), documentToken())
-	lexer.Add([]byte(`\."[^ "]+"`), pathToken(true))
-	lexer.Add([]byte(`\.[^ \}\{\:\[\],\|\.\[\(\)=]+`), pathToken(false))
-	lexer.Add([]byte(`\.`), selfToken())
-
-	lexer.Add([]byte(`\|`), opToken(Pipe))
-
-	lexer.Add([]byte(`-?\d+(\.\d+)`), floatValue())
-	lexer.Add([]byte(`-?[1-9](\.\d+)?[Ee][-+]?\d+`), floatValue())
-	lexer.Add([]byte(`-?\d+`), numberValue())
-
-	lexer.Add([]byte(`[Tt][Rr][Uu][Ee]`), booleanValue(true))
-	lexer.Add([]byte(`[Ff][Aa][Ll][Ss][Ee]`), booleanValue(false))
-
-	lexer.Add([]byte(`[Nn][Uu][Ll][Ll]`), nullValue())
-	lexer.Add([]byte(`~`), nullValue())
-
-	lexer.Add([]byte(`"[^"]*"`), stringValue(true))
-
-	lexer.Add([]byte(`\[`), literalToken(OpenCollect, false))
-	lexer.Add([]byte(`\]`), literalToken(CloseCollect, true))
-	lexer.Add([]byte(`\{`), literalToken(OpenCollectObject, false))
-	lexer.Add([]byte(`\}`), literalToken(CloseCollectObject, true))
-	lexer.Add([]byte(`\*`), opTokenWithPrefs(Multiply, nil, &MultiplyPreferences{AppendArrays: false}))
-	lexer.Add([]byte(`\*\+`), opTokenWithPrefs(Multiply, nil, &MultiplyPreferences{AppendArrays: true}))
-	lexer.Add([]byte(`\+`), opToken(Add))
-	lexer.Add([]byte(`\+=`), opToken(AddAssign))
-
-	err := lexer.Compile()
-	if err != nil {
-		return nil, err
-	}
-	return lexer, nil
-}
-
-type PathTokeniser interface {
-	Tokenise(path string) ([]*Token, error)
-}
-
-type pathTokeniser struct {
-	lexer *lex.Lexer
-}
-
-func NewPathTokeniser() PathTokeniser {
-	var lexer, err = initLexer()
-	if err != nil {
-		panic(err)
-	}
-	return &pathTokeniser{lexer}
-}
-
-func (p *pathTokeniser) Tokenise(path string) ([]*Token, error) {
-	scanner, err := p.lexer.Scanner([]byte(path))
-
-	if err != nil {
-		return nil, fmt.Errorf("Parsing expression: %v", err)
-	}
-	var tokens []*Token
-	for tok, err, eof := scanner.Next(); !eof; tok, err, eof = scanner.Next() {
-
-		if tok != nil {
-			token := tok.(*Token)
-			log.Debugf("Tokenising %v", token.toString())
-			tokens = append(tokens, token)
-		}
-		if err != nil {
-			return nil, fmt.Errorf("Parsing expression: %v", err)
-		}
-	}
-	var postProcessedTokens = make([]*Token, 0)
-
-	skipNextToken := false
-
-	for index := range tokens {
-		if skipNextToken {
-			skipNextToken = false
-		} else {
-			postProcessedTokens, skipNextToken = p.handleToken(tokens, index, postProcessedTokens)
-		}
-	}
-
-	return postProcessedTokens, nil
-}
-
-func (p *pathTokeniser) handleToken(tokens []*Token, index int, postProcessedTokens []*Token) (tokensAccum []*Token, skipNextToken bool) {
-	skipNextToken = false
-	token := tokens[index]
-
-	if token.TokenType == TraverseArrayCollect {
-		//need to put a traverse array then a collect token
-		// do this by adding traverse then converting token to collect
-
-		op := &Operation{OperationType: TraverseArray, StringValue: "TRAVERSE_ARRAY"}
-		postProcessedTokens = append(postProcessedTokens, &Token{TokenType: OperationToken, Operation: op})
-
-		token = &Token{TokenType: OpenCollect}
-
-	}
-
-	if index != len(tokens)-1 && token.AssignOperation != nil &&
-		tokens[index+1].TokenType == OperationToken &&
-		tokens[index+1].Operation.OperationType == Assign {
-		token.Operation = token.AssignOperation
-		token.Operation.UpdateAssign = tokens[index+1].Operation.UpdateAssign
-		skipNextToken = true
-	}
-
-	postProcessedTokens = append(postProcessedTokens, token)
-
-	if index != len(tokens)-1 && token.CheckForPostTraverse &&
-		tokens[index+1].TokenType == OperationToken &&
-		tokens[index+1].Operation.OperationType == TraversePath {
-		op := &Operation{OperationType: ShortPipe, Value: "PIPE"}
-		postProcessedTokens = append(postProcessedTokens, &Token{TokenType: OperationToken, Operation: op})
-	}
-	if index != len(tokens)-1 && token.CheckForPostTraverse &&
-		tokens[index+1].TokenType == OpenCollect {
-
-		op := &Operation{OperationType: ShortPipe, Value: "PIPE"}
-		postProcessedTokens = append(postProcessedTokens, &Token{TokenType: OperationToken, Operation: op})
-
-		op = &Operation{OperationType: TraverseArray}
-		postProcessedTokens = append(postProcessedTokens, &Token{TokenType: OperationToken, Operation: op})
-	}
-	if index != len(tokens)-1 && token.CheckForPostTraverse &&
-		tokens[index+1].TokenType == TraverseArrayCollect {
-
-		op := &Operation{OperationType: ShortPipe, Value: "PIPE"}
-		postProcessedTokens = append(postProcessedTokens, &Token{TokenType: OperationToken, Operation: op})
-
-	}
-	return postProcessedTokens, skipNextToken
-}
--- a/pkg/yqlib/printer.go
+++ b/pkg/yqlib/printer.go
@@ -24,6 +24,7 @@ type resultsPrinter struct {
 	previousDocIndex   uint
 	previousFileIndex  int
 	printedMatches     bool
+	treeNavigator      DataTreeNavigator
 }

 func NewPrinter(writer io.Writer, outputToJSON bool, unwrapScalar bool, colorsEnabled bool, indent int, printDocSeparators bool) Printer {
@@ -35,6 +36,7 @@ func NewPrinter(writer io.Writer, outputToJSON bool, unwrapScalar bool, colorsEn
 		indent:             indent,
 		printDocSeparators: printDocSeparators,
 		firstTimePrinting:  true,
+		treeNavigator:      NewDataTreeNavigator(),
 	}
 }

@@ -74,9 +76,9 @@ func (p *resultsPrinter) PrintResults(matchingNodes *list.List) error {
 	log.Debug("PrintResults for %v matches", matchingNodes.Len())
 	var err error
 	if p.outputToJSON {
-		explodeOp := Operation{OperationType: Explode}
-		explodeNode := PathTreeNode{Operation: &explodeOp}
-		matchingNodes, err = treeNavigator.GetMatchingNodes(matchingNodes, &explodeNode)
+		explodeOp := Operation{OperationType: explodeOpType}
+		explodeNode := ExpressionNode{Operation: &explodeOp}
+		matchingNodes, err = p.treeNavigator.GetMatchingNodes(matchingNodes, &explodeNode)
 		if err != nil {
 			return err
 		}
--- a/pkg/yqlib/stream_evaluator.go
+++ b/pkg/yqlib/stream_evaluator.go
@@ -8,24 +8,27 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )

+// A yaml expression evaluator that runs the expression multiple times for each given yaml document.
+// Uses less memory than loading all documents and running the expression once, but this cannot process
+// cross document expressions.
 type StreamEvaluator interface {
-	Evaluate(filename string, reader io.Reader, node *PathTreeNode, printer Printer) error
+	Evaluate(filename string, reader io.Reader, node *ExpressionNode, printer Printer) error
 	EvaluateFiles(expression string, filenames []string, printer Printer) error
 	EvaluateNew(expression string, printer Printer) error
 }

 type streamEvaluator struct {
 	treeNavigator DataTreeNavigator
-	treeCreator   PathTreeCreator
+	treeCreator   ExpressionParser
 	fileIndex     int
 }

 func NewStreamEvaluator() StreamEvaluator {
-	return &streamEvaluator{treeNavigator: NewDataTreeNavigator(), treeCreator: NewPathTreeCreator()}
+	return &streamEvaluator{treeNavigator: NewDataTreeNavigator(), treeCreator: NewExpressionParser()}
 }

 func (s *streamEvaluator) EvaluateNew(expression string, printer Printer) error {
-	node, err := treeCreator.ParsePath(expression)
+	node, err := s.treeCreator.ParseExpression(expression)
 	if err != nil {
 		return err
 	}
@@ -38,7 +41,7 @@ func (s *streamEvaluator) EvaluateNew(expression string, printer Printer) error
 	inputList := list.New()
 	inputList.PushBack(candidateNode)

-	matches, errorParsing := treeNavigator.GetMatchingNodes(inputList, node)
+	matches, errorParsing := s.treeNavigator.GetMatchingNodes(inputList, node)
 	if errorParsing != nil {
 		return errorParsing
 	}
@@ -47,7 +50,7 @@ func (s *streamEvaluator) EvaluateNew(expression string, printer Printer) error

 func (s *streamEvaluator) EvaluateFiles(expression string, filenames []string, printer Printer) error {

-	node, err := treeCreator.ParsePath(expression)
+	node, err := s.treeCreator.ParseExpression(expression)
 	if err != nil {
 		return err
 	}
@@ -70,7 +73,7 @@ func (s *streamEvaluator) EvaluateFiles(expression string, filenames []string, p
 	return nil
 }

-func (s *streamEvaluator) Evaluate(filename string, reader io.Reader, node *PathTreeNode, printer Printer) error {
+func (s *streamEvaluator) Evaluate(filename string, reader io.Reader, node *ExpressionNode, printer Printer) error {

 	var currentIndex uint

@@ -94,7 +97,7 @@ func (s *streamEvaluator) Evaluate(filename string, reader io.Reader, node *Path
 		inputList := list.New()
 		inputList.PushBack(candidateNode)

-		matches, errorParsing := treeNavigator.GetMatchingNodes(inputList, node)
+		matches, errorParsing := s.treeNavigator.GetMatchingNodes(inputList, node)
 		if errorParsing != nil {
 			return errorParsing
 		}
--- a/pkg/yqlib/utils.go
+++ b/pkg/yqlib/utils.go
@@ -9,9 +9,6 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )

-var treeNavigator = NewDataTreeNavigator()
-var treeCreator = NewPathTreeCreator()
-
 func readStream(filename string) (io.Reader, error) {
 	if filename == "-" {
 		return bufio.NewReader(os.Stdin), nil
--- a/pkg/yqlib/write_in_place_handler.go
+++ b/pkg/yqlib/write_in_place_handler.go
@@ -5,22 +5,22 @@ import (
 	"os"
 )

-type WriteInPlaceHandler interface {
+type writeInPlaceHandler interface {
 	CreateTempFile() (*os.File, error)
 	FinishWriteInPlace(evaluatedSuccessfully bool)
 }

-type writeInPlaceHandler struct {
+type writeInPlaceHandlerImpl struct {
 	inputFilename string
 	tempFile      *os.File
 }

-func NewWriteInPlaceHandler(inputFile string) WriteInPlaceHandler {
+func NewWriteInPlaceHandler(inputFile string) writeInPlaceHandler {

-	return &writeInPlaceHandler{inputFile, nil}
+	return &writeInPlaceHandlerImpl{inputFile, nil}
 }

-func (w *writeInPlaceHandler) CreateTempFile() (*os.File, error) {
+func (w *writeInPlaceHandlerImpl) CreateTempFile() (*os.File, error) {
 	info, err := os.Stat(w.inputFilename)
 	if err != nil {
 		return nil, err
@@ -46,7 +46,7 @@ func (w *writeInPlaceHandler) CreateTempFile() (*os.File, error) {
 	return file, err
 }

-func (w *writeInPlaceHandler) FinishWriteInPlace(evaluatedSuccessfully bool) {
+func (w *writeInPlaceHandlerImpl) FinishWriteInPlace(evaluatedSuccessfully bool) {
 	log.Debug("Going to write-inplace, evaluatedSuccessfully=%v, target=%v", evaluatedSuccessfully, w.inputFilename)
 	safelyCloseFile(w.tempFile)
 	if evaluatedSuccessfully {
--- a/snap/snapcraft.yaml
+++ b/snap/snapcraft.yaml
@@ -1,5 +1,5 @@
 name: yq
-version: '4.2.1'
+version: '4.3.2'
 summary: A lightweight and portable command-line YAML processor
 description: |
  The aim of the project is to be the jq or sed of yaml files.
Author	SHA1	Message	Date
Mike Farah	5c15936bf3	Incrementing version	2021-01-13 10:29:06 +11:00
Mike Farah	b0735d8152	Renaming pathtree to expression	2021-01-13 10:25:26 +11:00
Mike Farah	f17cbfd007	Removed global vars	2021-01-13 10:04:52 +11:00
Mike Farah	7b7ab70286	UnwrapDoc now private	2021-01-13 10:00:51 +11:00
Mike Farah	43165fa340	Moved eval function to eval interface	2021-01-13 09:35:57 +11:00
Mikhail Katychev	feda9f044d	added lib_test.go	2021-01-13 09:22:40 +11:00
Mikhail Katychev	85629af59c	added EvaluateNodes and EvaluateCandidateNodes to yqlib	2021-01-13 09:22:40 +11:00
Mike Farah	5fc26e9453	Merge now copies anchor names	2021-01-13 09:21:16 +11:00
Mike Farah	07a6fa4df5	Fixed creation of candidateNode in operators to include file metadata	2021-01-12 19:36:28 +11:00
Mike Farah	ec29ee7c14	Cleaning up exposed public api	2021-01-12 09:58:50 +11:00
Mike Farah	24538c0cc7	Fixed tag operator for top level node	2021-01-12 09:45:57 +11:00
Mike Farah	61398bfd3a	Fixed equals operator for top level node	2021-01-12 09:40:37 +11:00
Mike Farah	f7d95021c1	Fixed has operator for top level node	2021-01-12 09:30:24 +11:00
Mike Farah	6bb8b1fb77	fixing exposed functions and interfaces	2021-01-11 17:13:48 +11:00
Mike Farah	5e2c19cc86	fixing exposed functions and interfaces	2021-01-11 16:46:28 +11:00
Mike Farah	30c269a66c	Better add documentation	2021-01-11 15:52:06 +11:00
Mike Farah	70a1c60d7b	Added scalar addition	2021-01-11 15:43:50 +11:00
Mike Farah	e4d48bbc0d	Fixed collect at document level	2021-01-11 14:44:53 +11:00
Mike Farah	369ff94ad0	Better error handling will empty env	2021-01-11 14:38:53 +11:00
Mike Farah	1c7fb14631	Better recursive decent docs	2021-01-10 11:27:18 +11:00
Mike Farah	f4de5c4300	Better docIndex docs	2021-01-10 11:18:13 +11:00
Mike Farah	a72c14f06b	Better env docs	2021-01-10 11:09:59 +11:00
Mike Farah	5ed52aca66	Merged env commands in :eye-roll:	2021-01-10 10:51:23 +11:00
Mike Farah	5a5ac0dfef	Merge branch 'env_var'	2021-01-10 10:50:31 +11:00
Mike Farah	5a55869745	Bump version	2021-01-09 12:23:20 +11:00
Mike Farah	15e18bb98b	Error when passing files and using null-input flag	2021-01-09 12:23:06 +11:00
Mike Farah	644063646e	Env Ops!	2021-01-09 12:06:19 +11:00
Mike Farah	aabed1a237	strenv	2021-01-09 11:38:08 +11:00
Mike Farah	c12764dba8	wip	2021-01-08 21:09:43 +11:00
Mike Farah	1d5ecb244d	wip	2021-01-08 21:07:46 +11:00
Mike Farah	7798a141cf	Bumped go yaml for comment hanlding fixes	2021-01-08 20:56:54 +11:00
Mike Farah	b7583a538d	Added webi	2021-01-08 12:14:36 +11:00
Mike Farah	529e88b630	Added recurse examples	2021-01-08 12:11:29 +11:00
Mike Farah	658006eb93	Added another delete example	2021-01-08 11:59:49 +11:00
				`@@ -0,0 +1,2 @@`
				This operator is used to handle environment variables usage in path expressions. While environment variables can, of course, be passed in via your CLI with string interpolation, this often comes with complex quote escaping and can be tricky to write and read. Note that there are two forms, `env` which will parse the environment variable as a yaml (be it a map, array, string, number of boolean) and `strenv` which will always parse the argument as a string.