Regexp2 [api]

"Regexp2 is a feature-rich RegExp engine for Go. It doesn't have constant time guarantees like the built-in regexp package, but it allows backtracking and is compatible with Perl5 and .NET" - dlclark

Regexp2 Go library compiled with go2hx v0.1.0

Installation

haxelib git go2hx_regexp2 https://github.com/go2hx/regexp2

Add -lib go2hx_regexp2 to your hxml for openfl/haxeflixel users <haxelib name="go2hx_regexp2" />

Why use this?

Haxe regexp is target depedent certain features will work on one target and not another.

Take this example try.haxe:

function main() {
    var pattern = ~/^(abc|xyz)?(?(1)abc|xyz)/g;

    trace(pattern.match("abc"));
    trace(pattern.match("xyz"));
    trace(pattern.match("def"));
}

On js you get an error: invalid regexp group.

On hashlink or interp it works fine.

In order to get this and many other regexp patterns to work crossplatform you can use this library.

For example:

import github_dot_com.dlclark.regexp2.Regexp2;
function main() {
    final r = Regexp2.mustCompile("^(abc|xyz)?(?(1)abc|xyz)", 0);
    // left because it's a return tuple of (bool,error), right would give the error field
    trace(r.matchString("abc").left);
    trace(r.matchString("xyz").left);
    trace(r.matchString("def").left);
}

You can now target js with the given regex pattern and it will simply work!

Pretty cool eh?

RE2 compatibility mode

The default behavior of regexp2 is to match the .NET regexp engine, however the RE2 option is provided to change the parsing to increase compatibility with RE2. Using the RE2 option when compiling a regexp will not take away any features, but will change the following behaviors:

• add support for named ascii character classes (e.g. [[:foo:]])
• add support for python-style capture groups (e.g. (P<name>re))
• change singleline behavior for $ to only match end of string (like RE2) (see #24)
• change the character classes \d \s and \w to match the same characters as RE2. NOTE: if you also use the ECMAScript option then this will change the \s character class to match ECMAScript instead of RE2. ECMAScript allows more whitespace characters in \s than RE2 (but still fewer than the the default behavior).
• allow character escape sequences to have defaults. For example, by default \_ isn't a known character escape and will fail to compile, but in RE2 mode it will match the literal character _

Next steps

Run into an issue, feel free to make an issue detailing how to reproduce and the env being used (Haxe version, OS etc)

Interested in more libs like this?

Want to get involved in go2hx and/or the Haxe community, join the discord!