Regex

A toy regex implementation in roc.

It is far from feature complete, and probably doesn't follow any spec. I am just working on this to learn about regex, roc and language theory.

What is there

• Regex objects can be parsed from strings as in most programming languages.
• matches function which checks if a string matches a regex object (does not return the substring)

Supported regex syntax

• choices (with |)
• choice groups (with [])
• grouped regex expressions (with ())
• star operator (*)
• plus operator (+)
• question mark operator (?)

Plans

• choice group negation (with ^ in beginning of [])
• range expressions (with - in [])
• metacharacters (like ., \d, \w, ...)
• position anchors (like ^ and $, \b, \A and \Z, ...)

Non-plans

Some things I explicitly don't want to get into at the moment. This doesn't mean they won't ever get implemented, but it means it is not something I am interested in right now.

• Unicode support (for now only ascii. when not combined with operators, unicode should work)
• State machine (at the moment the implementation uses regex derivatives. to get a more performant engine, you would need to convert it to a state machine)
• High performance (This is a toy engine so I can learn)