X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Text%2FParserCombinators%2FReadPrec.hs;h=1fbada4c3b8eab8ec874246e33663ff7bc9c066f;hb=fcf4aa473708347cb25241cd6aa6547a05c51920;hp=bfb4fc2ee26c5e7541dcac924db4bd5b16eae42d;hpb=83022ae61d9138aa6c96f770bd374084481de954;p=ghc-base.git

diff --git a/Text/ParserCombinators/ReadPrec.hs b/Text/ParserCombinators/ReadPrec.hs
index bfb4fc2..1fbada4 100644
--- a/Text/ParserCombinators/ReadPrec.hs
+++ b/Text/ParserCombinators/ReadPrec.hs
@@ -7,41 +7,47 @@
 -- 
 -- Maintainer  :  libraries@haskell.org
 -- Stability   :  provisional
--- Portability :  portable
+-- Portability :  non-portable (uses Text.ParserCombinators.ReadP)
 --
+-- This library defines parser combinators for precedence parsing.
+
 -----------------------------------------------------------------------------
 
 module Text.ParserCombinators.ReadPrec
-  ( ReadPrec      -- :: * -> *; instance Functor, Monad, MonadPlus
+  ( 
+  ReadPrec,      -- :: * -> *; instance Functor, Monad, MonadPlus
   
   -- * Precedences
-  , Prec          -- :: *; = Int
-  , minPrec       -- :: Prec; = 0
+  Prec,          -- :: *; = Int
+  minPrec,       -- :: Prec; = 0
 
-  -- * Primitive operations
-  , lift          -- :: ReadP a -> ReadPrec a
-  , prec          -- :: Prec -> ReadPrec a -> ReadPrec a
-  , step          -- :: ReadPrec a -> ReadPrec a
-  , reset         -- :: ReadPrec a -> ReadPrec a
+  -- * Precedence operations
+  lift,          -- :: ReadP a -> ReadPrec a
+  prec,          -- :: Prec -> ReadPrec a -> ReadPrec a
+  step,          -- :: ReadPrec a -> ReadPrec a
+  reset,         -- :: ReadPrec a -> ReadPrec a
 
   -- * Other operations
-  , get           -- :: ReadPrec Char
-  , look          -- :: ReadPrec String
-  , (+++)         -- :: ReadPrec a -> ReadPrec a -> ReadPrec a
-  , pfail         -- :: ReadPrec a
-  , choice        -- :: [ReadPrec a] -> ReadPrec a
-
-  -- converters
-  , readPrec_to_P -- :: ReadPrec a       -> (Int -> ReadP a)
-  , readP_to_Prec -- :: (Int -> ReadP a) -> ReadPrec a
-  , readPrec_to_S -- :: ReadPrec a       -> (Int -> ReadS a)
-  , readS_to_Prec -- :: (Int -> ReadS a) -> ReadPrec a
+  -- All are based directly on their similarly-naned 'ReadP' counterparts.
+  get,           -- :: ReadPrec Char
+  look,          -- :: ReadPrec String
+  (+++),         -- :: ReadPrec a -> ReadPrec a -> ReadPrec a
+  (<++),         -- :: ReadPrec a -> ReadPrec a -> ReadPrec a
+  pfail,         -- :: ReadPrec a
+  choice,        -- :: [ReadPrec a] -> ReadPrec a
+
+  -- * Converters
+  readPrec_to_P, -- :: ReadPrec a       -> (Int -> ReadP a)
+  readP_to_Prec, -- :: (Int -> ReadP a) -> ReadPrec a
+  readPrec_to_S, -- :: ReadPrec a       -> (Int -> ReadS a)
+  readS_to_Prec, -- :: (Int -> ReadS a) -> ReadPrec a
   )
  where
 
 
 import Text.ParserCombinators.ReadP
   ( ReadP
+  , ReadS
   , readP_to_S
   , readS_to_P
   )
@@ -49,14 +55,15 @@ import Text.ParserCombinators.ReadP
 import qualified Text.ParserCombinators.ReadP as ReadP
   ( get
   , look
-  , (+++)
+  , (+++), (<++)
   , pfail
-  , choice
   )
 
 import Control.Monad( MonadPlus(..) )
+#ifdef __GLASGOW_HASKELL__
 import GHC.Num( Num(..) )
 import GHC.Base
+#endif
 
 -- ---------------------------------------------------------------------------
 -- The readPrec type
@@ -88,21 +95,22 @@ minPrec = 0
 -- Operations over ReadPrec
 
 lift :: ReadP a -> ReadPrec a
+-- ^ Lift a predence-insensitive 'ReadP' to a 'ReadPrec'
 lift m = P (\_ -> m)
 
 step :: ReadPrec a -> ReadPrec a
--- Increases the precedence context by one
+-- ^ Increases the precedence context by one
 step (P f) = P (\n -> f (n+1))
 
 reset :: ReadPrec a -> ReadPrec a
--- Resets the precedence context to zero
+-- ^ Resets the precedence context to zero
 reset (P f) = P (\n -> f minPrec)
 
 prec :: Prec -> ReadPrec a -> ReadPrec a
--- (prec n p) checks that the precedence context is 
+-- ^ @(prec n p)@ checks that the precedence context is 
 --			  less than or equal to n,
--- 	if not, fails
---	if so, parses p in context n
+--   * if not, fails
+--   * if so, parses p in context n
 prec n (P f) = P (\c -> if c <= n then f n else ReadP.pfail)
 
 -- ---------------------------------------------------------------------------
@@ -117,6 +125,9 @@ look = lift ReadP.look
 (+++) :: ReadPrec a -> ReadPrec a -> ReadPrec a
 P f1 +++ P f2 = P (\n -> f1 n ReadP.+++ f2 n)
 
+(<++) :: ReadPrec a -> ReadPrec a -> ReadPrec a
+P f1 <++ P f2 = P (\n -> f1 n ReadP.<++ f2 n)
+
 pfail :: ReadPrec a
 pfail = lift ReadP.pfail
 
@@ -126,10 +137,6 @@ choice ps = foldr (+++) pfail ps
 -- ---------------------------------------------------------------------------
 -- Converting between ReadPrec and Read
 
--- We define a local version of ReadS here,
--- because its "real" definition site is in GHC.Read
-type ReadS a = String -> [(a,String)]
-
 readPrec_to_P :: ReadPrec a -> (Int -> ReadP a)
 readPrec_to_P (P f) = f