sexp

S-Expression parsing/printing made fun and easy

Usage

sexp provides an S-expression data-type, and printers and parsers that work on all data-types that have Generic instances (so, everything you're ever likely to define yourself).

In order to encode/decode a custom data-type with sexp, 1) add a Generic instance for it, and 2) add an empty Sexpable instance for it. The default implementation of Sexpable's toSexp and fromSexp uses the Generic representation of the data-type to encode and decode it.

In order to print a Sexp, use printHum (for human-friendly output), or printMach (for human-unfriendly output). In order to parse a Sexp, use parse and friends.

See the documentation on Hackage for details.

% ghci
GHCi, version 7.6.2: http://www.haskell.org/ghc/  :? for help

λ > :set -XDeriveGeneric

λ > import Language.Sexp

λ > import GHC.Generics

λ > data MyType = Foo { unFoo :: Int, getBar :: Double } deriving ( Show, Generic )

λ > instance Sexpable MyType

λ > toSexp (Foo 23 42.0)
List [Atom "Foo",List [List [Atom "unFoo",Atom "23"],List [Atom "getBar",Atom "42.0"]]]

λ > printMach (toSexp (Foo 23 42.0))
"(Foo ((unFoo 23) (getBar \"42.0\")))"

λ > parseExn (printMach (toSexp (Foo 23 42.0)))
[List [Atom "Foo",List [List [Atom "unFoo",Atom "23"],List [Atom "getBar",Atom "42.0"]]]]

λ > fromSexp (head (parseExn (printMach (toSexp (Foo 23 42.0))))) :: Maybe MyType
Just (Foo {unFoo = 23, getBar = 42.0})

Installation

This package is on Hackage. To install it, run:

cabal update
cabal install sexp