Name:           funpat
Version:        0.1
Cabal-Version:  >= 1.8.0.2
License:        BSD3
License-File:   LICENSE
Author:         Gergely Devai
Maintainer:     deva@inf.elte.hu
Category:       Language
Build-type:     Simple
Stability:      experimental
Synopsis:       A generalization of pattern matching
Description:
    This library provides pattern matching with /restricted function patterns/
    (RFPs). An expression is an RFP iff exists an equivalent valid Haskell
    pattern. For example @(\"abc\" ++ xs)@ is an RFP, because @(\'a\' : \'b\' : \'c\' : xs)@
    is an equivalent valid Haskell pattern. On the other hand, @(xs ++ \"abc\")@
    is not an RFP. Details are discussed in the paper /Restricted Function Patterns/
    presented at /TFP 2011/.
    .
    /Example 1./ Here is a function to chop off the prefix @\"prefix\" of strings@:
    .
    @
    unprefix :: String -> String
    unprefix s = match s $ do
    \   with $ \\z ->   \"prefix\" ++ z ~> z
    \   with $ \\z ->   z             ~> z
    @
    .
    /Example 2./ Let's have a small embedded language:
    .
    @
    data Expr = Symbol String | Expr :$ Expr
    \    deriving (Eq,Show,Typeable)
    .
    instance Num Expr where
    \    fromInteger n = Symbol $ show n
    \    a + b = Symbol \"+\" :$ a :$ b
    \    a * b = Symbol \"*\" :$ a :$ b
    \    ...
    @
    .
    In order to allow pattern matching on expressions of type @Expr@, the
    following @Matchable@ instance is needed:
    .
    @
    instance Matchable Expr where
    \    Symbol s .=. Symbol z   = Just [s :=: z]
    \    (e :$ f) .=. (g :$ h)   = Just [e :=: g, f :=: h]
    \    _ .=. _                 = Nothing
    @
    .
    Now we can pattern match on expressions even if the constructors of
    the @Expr@ type were hidden:
    .
    @
    transform :: Expr -> Expr
    transform e = match e $ do
    \    with $ \\a ->        0 + a       ~> a
    \    with $ \\a b c ->    a * (b + c) ~> a * b + a * c
    \    with $ \\a ->        a           ~> a
    @
    
Library
  Build-Depends:
    base >= 4.2.0.2 && < 4.4,
    mtl >= 2.0.1.0 && <3
  Exposed-modules:
    Language.FunPat,
    Language.FunPat.Interface,
    Language.FunPat.Instances,
    Language.FunPat.Match
  Extensions:
    GADTs
    TypeFamilies
    FlexibleContexts
    DeriveDataTypeable