@hackage syntax0.3.0.0

syntax allows you to write a single syntax description and instantiate is both as a parser and a pretty printer.

The interface is based on a custom Functor/Applicative/Monad hierarchy, provided by the 'semi-iso' package. You fmap using a semi-isomorphism instead of function. A semi-isomorphism is a isomorphism that can fail in both directions, with slightly weakened laws. It is worth to note that Isos and Prisms from lens are valid semi-isomorphisms :)

Once you write a description you can, for example turn it into an Attoparsec parser, or into a Data.Syntax.Printer.Text.Printer.

See syntax-example and syntax-example-json for examples, syntax-attoparsec and syntax-printer for a parser/printer implementation.

The library was inspired by:

• Rendel, Tillmann, and Klaus Ostermann. "Invertible syntax descriptions: unifying parsing and pretty printing." ACM Sigplan Notices. Vol. 45. No. 11. ACM, 2010.

TODO:

• Research relative monads and relative monad transformers. Indent is basically a Reader monad over a syntax. How would a State monad look?

• Try to implement Haskell layout rule.

• Combinators for binary data formats, vectors.

• Better error messages.

• Maybe an implementation of do notation for SemiIsoMonad with QuasiQuoters, like the codo notation for comonads.