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Text.Read Portability portable Stability provisional Maintainer libraries@haskell.org

Contents

The Read class Haskell 98 functions New parsing functions

Description

The Text.Read library is the canonical library to import for Read-class facilities. It offers an extended and much improved Read class, which constitutes a proposed alternative to the Haskell98 Read. In particular, writing parsers is easier, and the parsers are much more efficient.

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 read :: (Read a) => String -> a readParen :: Bool -> ReadS a -> ReadS a lex :: ReadS String module Text.ParserCombinators.ReadPrec data Lexeme = Char Char | String String | Punc String | Ident String | Symbol String | Int Integer | Rat Rational | EOF lexP :: ReadPrec Lexeme readListDefault :: (Read a) => ReadS [a] readListPrecDefault :: (Read a) => ReadPrec [a]

The Read class

class Read a where

Methods readsPrec :: Int -> ReadS a readList :: ReadS [a] readPrec :: ReadPrec a readListPrec :: ReadPrec [a] Instances 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 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 StdGen

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.

Haskell 98 functions

reads :: (Read a) => ReadS a

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

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

lex :: ReadS String

New parsing functions

module Text.ParserCombinators.ReadPrec

data Lexeme

Constructors Char Char String String Punc String Ident String Symbol String Int Integer Rat Rational EOF Instances Read Lexeme

lexP :: ReadPrec Lexeme

Parse a single lexeme

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

Use this to define the readList method, if you don't want a special case

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

Use this to define the readListPrec method, if you don't want a special case

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