Probabilistic regular expressions

• Kleene star (and +) use geometric distributions on length.
• Currently, score returns likelihood of most probable execution trace, rather than marginalising.
• Add new primitives with Wrapper class
• Primitives may be stateful (so log p(/AA/->xx) is not necessarily 2 * log p(/A/->x))

Usage:

import pregex as pre
r = pre.create("\\d+\\l+\\u+\\s")
samp = r.sample() //'3gclxbZ\t'
score = r.match("123abcABC ") //-34.486418601378595

• Compare with Dijkstra's algorithm for MAP, maybe it's faster?
• Make differentiable character class
• use separate bracket types for each function?
• 'sample' and 'marginalise' modes. Note -- for this, KleeneStar needs to be adapted to get correct score for fo?* -> foo. First calculate probability q=P(o?->ε), then multiply all partialmatches by 1/[1-q(1-p))]
• Should still be able to do dynamic programming to combine partialMatches that have different states, so long as the difference in state doesn't affect the continuation
• Replace namedtuples with attrs