An attoparsec roundtrip

mit, parsing, text, Propose Tags , Data.Attoparsec.Unparse, Data.Attoparsec.Unparse.Printer, Data.Attoparsec.Unparse.Profunctor
cabal install unparse-attoparsec-


Unparse attoparsec

Define an attoparsec parser, get a DRY printer.

This library essentially defines two types:

  • Parser :: * -> * -> *, a wrapper around attoparsec's own Parser :: * -> *;
  • Printer :: * -> * -> *, a type which does the inverse of a parser;

and a type class Attoparsec, instantiated by Parser and Printer, wrapping attoparsec's core operations (including lookaheads!).

Programming polymorphically under an Attoparsec p constraint yields a DRY specification of both a parser and a printer.

Monadic and applicative composition can be used under a ForallF Monad p constraint (resp. ForallF Applicative p), meaning that for all types x, the type p x is an instance of Monad (resp. Applicative). These constraints are made possible thanks to the constraints package. The profunctor-monad package (not yet available; see src/Data/Attoparsec/Unparse/Profunctor.hs) provides convenient ways to work with them (with or rebindable syntax).


Simply clone the repo' and build with stack:

stack install --test


Check out example/AesonParser.hs