module Text.Read (
Read(..),
ReadS,
reads,
read,
readParen,
lex,
#if defined(__GLASGOW_HASKELL__) || defined(__HUGS__)
module Text.ParserCombinators.ReadPrec,
L.Lexeme(..),
lexP,
parens,
#endif
#ifdef __GLASGOW_HASKELL__
readListDefault,
readListPrecDefault,
#endif
) 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
import qualified Text.Read.Lex as L
#endif
#ifdef __HUGS__
lexP :: ReadPrec L.Lexeme
lexP = lift L.lex
parens :: ReadPrec a -> ReadPrec a
parens p = optional
where
optional = p +++ mandatory
mandatory = do
L.Punc "(" <- lexP
x <- reset optional
L.Punc ")" <- lexP
return x
#endif
#ifdef __GLASGOW_HASKELL__
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
read :: Read a => String -> a
read s = either error id (readEither s)
#endif
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