[project @ 2003-07-31 17:45:22 by ross]

[ghc-base.git] / Text / ParserCombinators / Parsec / Perm.hs

diff --git a/Text/ParserCombinators/Parsec/Perm.hs b/Text/ParserCombinators/Parsec/Perm.hs
deleted file mode 100644 (file)
index cbdbfe0..0000000
--- a/Text/ParserCombinators/Parsec/Perm.hs
+++ /dev/null
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------------------------------------------------------------------------------
--- |
--- Module      :  Text.ParserCombinators.Parsec.Perm
--- Copyright   :  (c) Daan Leijen 1999-2001
--- License     :  BSD-style (see the file libraries/base/LICENSE)
--- 
--- Maintainer  :  daan@cs.uu.nl
--- Stability   :  provisional
--- Portability :  non-portable (uses existentially quantified data constructors)
---
--- This module implements permutation parsers. The algorithm used
--- is fairly complex since we push the type system to its limits :-)
--- The algorithm is described in:
---
--- /Parsing Permutation Phrases,/
--- by Arthur Baars, Andres Loh and Doaitse Swierstra.
--- Published as a functional pearl at the Haskell Workshop 2001.
--- 
------------------------------------------------------------------------------
-
-module Text.ParserCombinators.Parsec.Perm
-                  ( PermParser  -- abstract
-
-                  , permute
-                  , (<||>), (<$$>)
-                  , (<|?>), (<$?>)
-                  ) where
-
-import Text.ParserCombinators.Parsec
-
-{---------------------------------------------------------------
-
----------------------------------------------------------------}
-infixl 1 <||>, <|?>
-infixl 2 <$$>, <$?>
-
-
-{---------------------------------------------------------------
-  test -- parse a permutation of 
-  * an optional string of 'a's
-  * a required 'b'
-  * an optional 'c'
----------------------------------------------------------------}
-test input
-  = parse (do{ x <- ptest; eof; return x }) "" input
-
-ptest :: Parser (String,Char,Char)
-ptest  
-  = permute $
-    (,,) <$?> ("",many1 (char 'a'))
-         <||> char 'b' 
-         <|?> ('_',char 'c')
-
-
-{---------------------------------------------------------------
-  Building a permutation parser
----------------------------------------------------------------}
-(<||>) :: PermParser tok st (a -> b) -> GenParser tok st a -> PermParser tok st b
-(<||>) perm p     = add perm p                  
-(<$$>) f p        = newperm f <||> p
-
-(<|?>) perm (x,p) = addopt perm x p
-(<$?>) f (x,p)    = newperm f <|?> (x,p)
-
-
-
-{---------------------------------------------------------------
-  The permutation tree
----------------------------------------------------------------}
-data PermParser tok st a = Perm (Maybe a) [Branch tok st a]
-data Branch tok st a     = forall b. Branch (PermParser tok st (b -> a)) (GenParser tok st b)
-
-
--- transform a permutation tree into a normal parser
-permute :: PermParser tok st a -> GenParser tok st a
-permute (Perm def xs)
-  = choice (map branch xs ++ empty)
-  where
-    empty
-      = case def of
-          Nothing -> []
-          Just x  -> [return x]
-
-    branch (Branch perm p)
-      = do{ x <- p
-          ; f <- permute perm
-          ; return (f x)
-          }
-
--- build permutation trees
-newperm :: (a -> b) -> PermParser tok st (a -> b)
-newperm f
-  = Perm (Just f) []
-
-add :: PermParser tok st (a -> b) -> GenParser tok st a -> PermParser tok st b
-add perm@(Perm mf fs) p
-  = Perm Nothing (first:map insert fs)
-  where
-    first   = Branch perm p
-    insert (Branch perm' p')
-            = Branch (add (mapPerms flip perm') p) p'
-
-addopt :: PermParser tok st (a -> b) -> a -> GenParser tok st a -> PermParser tok st b
-addopt perm@(Perm mf fs) x p
-  = Perm (fmap ($ x) mf) (first:map insert fs)
-  where
-    first   = Branch perm p
-    insert (Branch perm' p')
-            = Branch (addopt (mapPerms flip perm') x p) p'
-
-
-mapPerms :: (a -> b) -> PermParser tok st a -> PermParser tok st b
-mapPerms f (Perm x xs)
-  = Perm (fmap f x) (map (mapBranch f) xs)
-  where
-    mapBranch f (Branch perm p)
-      = Branch (mapPerms (f.) perm) p