GitHub - mrkkrp/megaparsec: Industrial-strength monadic parser combinator library

The package is built around MonadParsec, an MTL-style monad transformer. Most features work with all instances of MonadParsec. One can achieve various effects combining monad transformers, i.e. building a monadic stack. Since the common monad transformers like WriterT, StateT, ReaderT and others are instances of the MonadParsec type class, one can also wrap ParsecT in these monads, achieving, for

[masterq]

今使うならParsecではなくこちらとのこと

[igrep]

“a fork of Parsec library originally written by Daan Leijen.”