Port regextract DSL function from C to Go

go/src/dsl/cst/builtin_function_manager.go

@@ -335,8 +335,6 @@ regex-match operator: try '$y = ~$x'.`,
 	// FUNC_CLASS_STRING
 
 	// TODO:
-	// regextract : help: `Example: '$name=regextract($name, "[A-Z]{3}[0-9]{2}")'`,
-	// regextract_or_else : help: `Example: '$name=regextract_or_else($name, "[A-Z]{3}[0-9]{2}", "default")'`,
 	// system : help: `Run command string, yielding its stdout minus final carriage return.
 
 	{
@@ -381,6 +379,20 @@ regex-match operator: try '$y = ~$x'.`,
 		unaryFunc: types.MlrvalLStrip,
 	},
 
+	{
+		name:       "regextract",
+		class:      FUNC_CLASS_STRING,
+		help:       `Example: '$name=regextract($name, "[A-Z]{3}[0-9]{2}")'`,
+		binaryFunc: types.MlrvalRegextract,
+	},
+
+	{
+		name:        "regextract_or_else",
+		class:       FUNC_CLASS_STRING,
+		help:        `Example: '$name=regextract_or_else($name, "[A-Z]{3}[0-9]{2}", "default")'`,
+		ternaryFunc: types.MlrvalRegextractOrElse,
+	},
+
 	{
 		name:      "rstrip",
 		class:     FUNC_CLASS_STRING,

go/src/lib/regex.go

@@ -3,6 +3,7 @@ package lib
 import (
 	"errors"
 	"fmt"
+	"os"
 	"regexp"
 	"strings"
 )
@@ -14,7 +15,7 @@ import (
 // * If the regex_string is of the form a.*b, compiles it using cflags without REG_ICASE.
 // * If the regex_string is of the form "a.*b", compiles a.*b using cflags without REG_ICASE.
 // * If the regex_string is of the form "a.*b"i, compiles a.*b using cflags with REG_ICASE.
-func CompilerMillerRegex(regexString string) (*regexp.Regexp, error) {
+func CompileMillerRegex(regexString string) (*regexp.Regexp, error) {
 	if !strings.HasPrefix(regexString, "\"") {
 		return regexp.Compile(regexString)
 	} else {
@@ -41,3 +42,12 @@ func CompilerMillerRegex(regexString string) (*regexp.Regexp, error) {
 		}
 	}
 }
+
+func CompileMillerRegexOrDie(regexString string) *regexp.Regexp {
+	regex, err := CompileMillerRegex(regexString)
+	if err != nil {
+		fmt.Fprint(os.Stderr, err)
+		os.Exit(1)
+	}
+	return regex
+}

go/src/transformers/having-fields.go

@@ -180,7 +180,7 @@ func NewTransformerHavingFields(
 	} else {
 		// Let them type in a.*b if they want, or "a.*b", or "a.*b"i.
 		// Strip off the leading " and trailing " or "i.
-		regex, err := lib.CompilerMillerRegex(regexString)
+		regex, err := lib.CompileMillerRegex(regexString)
 		if err != nil {
 			fmt.Fprintf(
 				os.Stderr,

go/src/types/mlrval_functions_regex.go

@@ -1,8 +1,9 @@
 package types
 
 import (
-	"regexp"
 	"strings"
+
+	"miller/src/lib"
 )
 
 // ================================================================
@@ -53,7 +54,7 @@ func MlrvalSub(ma, mb, mc *Mlrval) Mlrval {
 		return MlrvalFromError()
 	}
 	// TODO: better exception-handling
-	re := regexp.MustCompile(mb.printrep)
+	re := lib.CompileMillerRegexOrDie(mb.printrep)
 
 	onFirst := true
 	output := re.ReplaceAllStringFunc(ma.printrep, func(s string) string {
@@ -90,7 +91,7 @@ func MlrvalGsub(ma, mb, mc *Mlrval) Mlrval {
 		return MlrvalFromError()
 	}
 	// TODO: better exception-handling
-	re := regexp.MustCompile(mb.printrep)
+	re := lib.CompileMillerRegexOrDie(mb.printrep)
 	return MlrvalFromString(
 		re.ReplaceAllString(ma.printrep, mc.printrep),
 	)
@@ -113,7 +114,7 @@ func MlrvalStringMatchesRegexp(ma, mb *Mlrval) Mlrval {
 		return MlrvalFromError()
 	}
 	// TODO: better exception-handling
-	re := regexp.MustCompile(mb.printrep)
+	re := lib.CompileMillerRegexOrDie(mb.printrep)
 	return MlrvalFromBool(
 		re.MatchString(ma.printrep),
 	)
@@ -127,3 +128,38 @@ func MlrvalStringDoesNotMatchRegexp(ma, mb *Mlrval) Mlrval {
 		return matches // error, absent, etc.
 	}
 }
+
+// TODO: find a way to keep and stash a precompiled regex, somewhere in the CST ...
+func MlrvalRegextract(ma, mb *Mlrval) Mlrval {
+	if !ma.IsString() {
+		return MlrvalFromError()
+	}
+	if !mb.IsString() {
+		return MlrvalFromError()
+	}
+	regex := lib.CompileMillerRegexOrDie(mb.printrep)
+	// TODO: See if we need FindStringIndex or FindStringSubmatch to distinguish from matching "".
+	output := regex.FindString(ma.printrep)
+	if output != "" {
+		return MlrvalFromString(output)
+	} else {
+		return MlrvalFromAbsent()
+	}
+}
+
+func MlrvalRegextractOrElse(ma, mb, mc *Mlrval) Mlrval {
+	if !ma.IsString() {
+		return MlrvalFromError()
+	}
+	if !mb.IsString() {
+		return MlrvalFromError()
+	}
+	regex := lib.CompileMillerRegexOrDie(mb.printrep)
+	// TODO: See if we need FindStringIndex or FindStringSubmatch to distinguish from matching "".
+	output := regex.FindString(ma.printrep)
+	if output != "" {
+		return MlrvalFromString(output)
+	} else {
+		return *mc
+	}
+}

go/todo.txt

@@ -118,7 +118,6 @@ no need to bootstrap a parser for the parser-generator language
 * stats1:
   o actualize -S and -F -- ?
   o regexed
-    - needs implementation of "a.*b"i
 
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 ! JSON null needs to be passed through as-is ... somehow ... new mlrval type??