Compatibility issue with NKo Digits

[tschaub]

It looks like \d matches ߀ (\u07c0) with regexp2, but not with the standard library regexp.

See the following example:

package main

import (
	"fmt"
	"regexp"

	"github.com/dlclark/regexp2"
)

func main() {
	re := regexp.MustCompile(`^\d$`)
	re2 := regexp2.MustCompile(`^\d$`, regexp2.RE2)

	notZero := "߀" // \u07c0

	match := re.MatchString(notZero)
	fmt.Printf("regexp: %v\n", match)

	match2, _ := re2.MatchString(notZero)
	fmt.Printf("regexp2: %v\n", match2)
}

Perhaps this is a known issue, but I'm wondering if there is a way to get additional compatibility with the standard library.

[tschaub]

I missed the regexp2.ECMAScript option. Looks like compiling with this option is what I'm after. Thanks for the work on this library.

[dlclark]

No problem. The ECMAScript option does change the character classes to match ECMAScript/JavaScript and it just so happens that ECMAScript \d and \w matches the same chars as Go's RE2 engine. However, \s does not contain the exact same chars in RE2 and ECMAScript.

It makes sense to use the RE2 char class definitions for all 6 (\s \w \d plus negates) if option RE2 is used. Forcing the ECMAScript option isn't ideal.

Thanks for bringing it up.