Re-implementing redgrep in Haskell. With an Applicative interface. (Or at least an non-monadic one.)
This is a regular expression matcher that also support intersection and complement in addition to the traditional regular expression operations.
It is also a proper parser, so perhaps I will add sed-like functionality.
In future, like redgrep, I plan to support compilation to llvm. The matching functionality right now, is only a proof of concept, and doesn't make any performance claims.
See https://github.com/google/redgrep for the original.