Zig Regex

A fairly quick regex implementation done a while back for learning purposes, I'll just clean it up and put it out there. This one is largely implemented with tagged unions and recursive descent rather than a state machine or a byte gobbler so it shows you actually can write zig programs in a fairly functional manner.

In fact it's pretty damn nice for it.

You can test the library with

zig test gregex.zig

Usecases can be found in the .zig file itself,

but here's a simple usecase.

    var test_restr = "name: *(.*)\\((.*)\\)$";

    var find = try re_find_once(test_restr, "date: 2077-06-24 name: adam jensen (occupation: killa)\n", alloc);
    defer find.deinit(); // find has an arraylist of regex objects, this should be de-initialized when out of scope.

    print("{s}\n", .{ find.text }); // This will print out the entire string
    
    // the result supports groups
    print("find.groups.items[1] = '{s}':\n", .{find.groups.items[0].text});
    print("find.groups.items[2] = '{s}':\n", .{find.groups.items[0].text});

in terms of sequences, a few of the most commonly supported sequences are supported.

• *, +, ? : capture mode operators, respectively; zero or more, one or more, zero or one
• () : create a match group (does not support nesting)
• []: or match group (match any union of elements within)
• a-z: sequence range match
• predefined semantic groups:
  • \s : whitespace (capital version is inverted)
  • \w : alphanumeric
  • \d : digits
• !: Single term negation negates matches that are a single term. does not work on () groups or. but will work on or-groups.
  • negative look-ahead is not supported.

Note: this is the first thing I've ever actually written in zig so there's a few growing pains in visible in the code.