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][sexp] 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][sexp].  To install it, run:

    cabal update
    cabal install sexp

[sexp]: http://hackage.haskell.org/package/sexp