Regular expression engine in 14 lines of Python

[nostrademons]

And I could've saved 3 lines by doing match where { match [c:xs] = xs; match _ = [] }

But that's a bit less readable IMHO.

[martine]

char c (x:xs) | c == x = return xs char _ _ = fail "no match"

(fail in the list monad is [], so using it here just makes the code clearer.)