Implement regular expression library (re)

[swenson]

Most of re is written in C in CPython, meaning we have to find an alternative.

One possibility is PyPy's implementation, which appears to be mostly written in RPython:

https://bitbucket.org/pypy/pypy/src/b0e70c0c2ac0d1b8a066b64eb94bd3b858a9be8f/rpython/rlib/rsre/?at=default

We could possibly, with some modifications, load this, similarly to how we load in ouroboros modules.

[ElSaico]

Well, there is JavaScript's native RegExp... though converting Python's extensions to its syntax would be hard work anyway. (and, amusingly enough, would require extra regexes)

[ElSaico]

Taking the old sre module from Python <= 2.4 and backporting later stuff is also an option.

[swenson]

Is the sre module from Python <= 2.4 written in pure Python? If so, I'd definitely be into that as a start. Even if we aren't 100% compatible with the latest stuff, getting basic re working would be a huge step.

[ElSaico]

It is!

And the only hard new part seems to be the flags thing; everything else looks trivial.

[swenson]

Awesome! I'd love to see some work on that then :)