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GHC.Read Portability non-portable (GHC Extensions) Stability internal Maintainer cvs-ghc@haskell.org

Description

The Read class and instances for basic data types.

Synopsis

class Read a where readsPrec :: Int -> ReadS a readList :: ReadS [a] readPrec :: ReadPrec a readListPrec :: ReadPrec [a] type ReadS a = String -> [(a, String)] reads :: (Read a) => ReadS a readp :: (Read a) => ReadP a readEither :: (Read a) => String -> Either String a read :: (Read a) => String -> a lex :: ReadS String lexLitChar :: ReadS String readLitChar :: ReadS Char lexDigits :: ReadS String lexP :: ReadPrec Lexeme paren :: ReadPrec a -> ReadPrec a parens :: ReadPrec a -> ReadPrec a list :: ReadPrec a -> ReadPrec [a] choose :: [(String, ReadPrec a)] -> ReadPrec a readListDefault :: (Read a) => ReadS [a] readListPrecDefault :: (Read a) => ReadPrec [a] readParen :: Bool -> ReadS a -> ReadS a

Documentation

class Read a where

Methods readsPrec :: Int -> ReadS a readList :: ReadS [a] readPrec :: ReadPrec a Proposed replacement for readsPrec using new-style parsers (GHC only). readListPrec :: ReadPrec [a] Proposed replacement for readList using new-style parsers (GHC only). Instances (RealFloat a, Read a) => Read (Complex a) Read CChar Read CSChar Read CUChar Read CShort Read CUShort Read CInt Read CUInt Read CLong Read CULong Read CLLong Read CULLong Read CFloat Read CDouble Read CLDouble Read CPtrdiff Read CSize Read CWchar Read CSigAtomic Read CClock Read CTime Read IOModeEx Read SeekMode Read BufferMode Read ExitCode Read IOMode Read Int8 Read Int16 Read Int32 Read Int64 Read Char Read Bool Read Ordering (Read a) => Read (Maybe a) (Read a, Read b) => Read (Either a b) (Read a) => Read [a] (Ix a, Read a, Read b) => Read (Array a b) Read Lexeme Read Int Read Integer Read Float Read Double (Integral a, Read a) => Read (Ratio a) Read () (Read a, Read b) => Read (a, b) (Read a, Read b, Read c) => Read (a, b, c) (Read a, Read b, Read c, Read d) => Read (a, b, c, d) (Read a, Read b, Read c, Read d, Read e) => Read (a, b, c, d, e) Read Word Read Word8 Read Word16 Read Word32 Read Word64 Read Permissions Read CDev Read CIno Read CMode Read COff Read CPid Read CSsize Read CGid Read CNlink Read CUid Read CCc Read CSpeed Read CTcflag Read CRLim Read Fd Read StdGen Read Month Read Day Read CalendarTime Read TimeDiff

type ReadS a = String -> [(a, String)]

A parser for a type a, represented as a function that takes a String and returns a list of possible parses (a,String) pairs.

reads :: (Read a) => ReadS a

readp :: (Read a) => ReadP a

readEither :: (Read a) => String -> Either String a

read :: (Read a) => String -> a

lex :: ReadS String

lexLitChar :: ReadS String

readLitChar :: ReadS Char

lexDigits :: ReadS String

lexP :: ReadPrec Lexeme

Parse a single lexeme

paren :: ReadPrec a -> ReadPrec a

(paren p) parses "(P0)" where p parses "P0" in precedence context zero

parens :: ReadPrec a -> ReadPrec a

(parens p) parses "P", "(P0)", "((P0))", etc, where p parses "P" in the current precedence context parses "P0" in precedence context zero

list :: ReadPrec a -> ReadPrec [a]

(list p) parses a list of things parsed by p, using the usual square-bracket syntax.

choose :: [(String, ReadPrec a)] -> ReadPrec a

Parse the specified lexeme and continue as specified. Esp useful for nullary constructors; e.g. choose [("A", return A), ("B", return B)]

readListDefault :: (Read a) => ReadS [a]

Use this to define the readList method, if you don't want a special case (GHC only; for other systems the default suffices).

readListPrecDefault :: (Read a) => ReadPrec [a]

Use this to define the readListPrec method, if you don't want a special case (GHC only).

readParen :: Bool -> ReadS a -> ReadS a

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