Move some bits around to stop Data.Either being in the base import knot

diff --git a/Data/Either.hs b/Data/Either.hs
index cb71eaa..956e6da 100644 (file)
--- a/Data/Either.hs
+++ b/Data/Either.hs
@@ -21,9 +21,13 @@ module Data.Either (
    partitionEithers, -- :: [Either a b] -> ([a],[b])
  ) where
 
+#include "Typeable.h"
+
 #ifdef __GLASGOW_HASKELL__
 import GHC.Base
 import GHC.Show
+import GHC.Read
+import Data.Typeable
 
 {-
 -- just for testing
@@ -40,7 +44,7 @@ either correct or an error; by convention, the 'Left' constructor is
 used to hold an error value and the 'Right' constructor is used to
 hold a correct value (mnemonic: \"right\" also means \"correct\").
 -}
-data  Either a b  =  Left a | Right b   deriving (Eq, Ord, Show)
+data  Either a b  =  Left a | Right b   deriving (Eq, Ord, Read, Show)
 
 -- | Case analysis for the 'Either' type.
 -- If the value is @'Left' a@, apply the first function to @a@;
@@ -50,6 +54,8 @@ either f _ (Left x)     =  f x
 either _ g (Right y)    =  g y
 #endif  /* __GLASGOW_HASKELL__ */
 
+INSTANCE_TYPEABLE2(Either,eitherTc,"Either")
+
 -- | Extracts from a list of 'Either' all the 'Left' elements
 -- All the 'Left' elements are extracted in order.
 

diff --git a/Data/Typeable.hs b/Data/Typeable.hs
index aae61fe..cad0b78 100644 (file)
--- a/Data/Typeable.hs
+++ b/Data/Typeable.hs
@@ -83,7 +83,6 @@ module Data.Typeable
 
 import qualified Data.HashTable as HT
 import Data.Maybe
-import Data.Either
 import Data.Int
 import Data.Word
 import Data.List( foldl, intersperse )
@@ -487,7 +486,6 @@ INSTANCE_TYPEABLE0((),unitTc,"()")
 INSTANCE_TYPEABLE1([],listTc,"[]")
 INSTANCE_TYPEABLE1(Maybe,maybeTc,"Maybe")
 INSTANCE_TYPEABLE1(Ratio,ratioTc,"Ratio")
-INSTANCE_TYPEABLE2(Either,eitherTc,"Either")
 INSTANCE_TYPEABLE2((->),funTc,"->")
 INSTANCE_TYPEABLE1(IO,ioTc,"IO")
 

diff --git a/GHC/Read.lhs b/GHC/Read.lhs
index 769e055..b890b46 100644 (file)
--- a/GHC/Read.lhs
+++ b/GHC/Read.lhs
@@ -22,12 +22,6 @@ module GHC.Read
   -- ReadS type
   , ReadS      -- :: *; = String -> [(a,String)]
 
-  -- utility functions
-  , reads      -- :: Read a => ReadS a
-  , readp      -- :: Read a => ReadP a
-  , readEither -- :: Read a => String -> Either String a
-  , read       -- :: Read a => String -> a
-
   -- H98 compatibility
   , lex         -- :: ReadS String
   , lexLitChar  -- :: ReadS String
@@ -44,6 +38,9 @@ module GHC.Read
 
   -- Temporary
   , readParen
+
+  -- XXX Can this be removed?
+  , readp
   )
  where
 
@@ -64,7 +61,6 @@ import qualified Text.Read.Lex as L
 import Text.ParserCombinators.ReadPrec
 
 import Data.Maybe
-import Data.Either
 
 #ifndef __HADDOCK__
 import {-# SOURCE #-} GHC.Unicode       ( isDigit )
@@ -225,33 +221,6 @@ readListPrecDefault :: Read a => ReadPrec [a]
 readListPrecDefault = list readPrec
 
 ------------------------------------------------------------------------
--- utility functions
-
--- | equivalent to 'readsPrec' with a precedence of 0.
-reads :: Read a => ReadS a
-reads = readsPrec minPrec
-
-readp :: Read a => ReadP a
-readp = readPrec_to_P readPrec minPrec
-
-readEither :: Read a => String -> Either String a
-readEither s =
-  case [ x | (x,"") <- readPrec_to_S read' minPrec s ] of
-    [x] -> Right x
-    []  -> Left "Prelude.read: no parse"
-    _   -> Left "Prelude.read: ambiguous parse"
- where
-  read' =
-    do x <- readPrec
-       lift P.skipSpaces
-       return x
-
--- | The 'read' function reads input from a string, which must be
--- completely consumed by the input process.
-read :: Read a => String -> a
-read s = either error id (readEither s)
-
-------------------------------------------------------------------------
 -- H98 compatibility
 
 -- | The 'lex' function reads a single lexeme from the input, discarding
@@ -448,23 +417,6 @@ instance Read a => Read (Maybe a) where
   readListPrec = readListPrecDefault
   readList     = readListDefault
 
-instance (Read a, Read b) => Read (Either a b) where
-  readPrec =
-    parens
-    ( prec appPrec
-      ( do L.Ident "Left" <- lexP
-           x            <- step readPrec
-           return (Left x)
-       +++
-        do L.Ident "Right" <- lexP
-           y             <- step readPrec
-           return (Right y)
-      )
-    )
-
-  readListPrec = readListPrecDefault
-  readList     = readListDefault
-
 instance Read a => Read [a] where
   readPrec     = readListPrec
   readListPrec = readListPrecDefault
@@ -714,3 +666,11 @@ instance (Read a, Read b, Read c, Read d, Read e, Read f, Read g, Read h,
   readListPrec = readListPrecDefault
   readList     = readListDefault
 \end{code}
+
+\begin{code}
+-- XXX Can this be removed?
+
+readp :: Read a => ReadP a
+readp = readPrec_to_P readPrec minPrec
+\end{code}
+

diff --git a/Text/Read.hs b/Text/Read.hs
index 172a4c2..5ab8877 100644 (file)
--- a/Text/Read.hs
+++ b/Text/Read.hs
@@ -45,7 +45,10 @@ module Text.Read (
  ) where
 
 #ifdef __GLASGOW_HASKELL__
+import GHC.Base
 import GHC.Read
+import Data.Either
+import Text.ParserCombinators.ReadP as P
 #endif
 #if defined(__GLASGOW_HASKELL__) || defined(__HUGS__)
 import Text.ParserCombinators.ReadPrec
@@ -68,3 +71,30 @@ parens p = optional
     L.Punc ")" <- lexP
     return x
 #endif
+
+#ifdef __GLASGOW_HASKELL__
+------------------------------------------------------------------------
+-- utility functions
+
+-- | equivalent to 'readsPrec' with a precedence of 0.
+reads :: Read a => ReadS a
+reads = readsPrec minPrec
+
+readEither :: Read a => String -> Either String a
+readEither s =
+  case [ x | (x,"") <- readPrec_to_S read' minPrec s ] of
+    [x] -> Right x
+    []  -> Left "Prelude.read: no parse"
+    _   -> Left "Prelude.read: ambiguous parse"
+ where
+  read' =
+    do x <- readPrec
+       lift P.skipSpaces
+       return x
+
+-- | The 'read' function reads input from a string, which must be
+-- completely consumed by the input process.
+read :: Read a => String -> a
+read s = either error id (readEither s)
+#endif
+