Parsec (parser)

Parsec is a library for writing parsers in Haskell. It is based on higher-order parser combinators, so a complicated parser can be made out of many smaller ones. It has been reimplemented in many other languages, including Erlang, OCaml, F# and C#, as well as imperative languages such as Java.

Because a parser combinator-based program is generally slower than a parser generator-based program, Parsec is normally used for small domain-specific languages, while Happy is used for compilers such as GHC.