base-4.6.0.1: Basic libraries

Portabilitynon-portable (uses Text.ParserCombinators.ReadP)
Stabilityprovisional
Maintainerlibraries@haskell.org
Safe HaskellTrustworthy

Text.ParserCombinators.ReadPrec

Contents

Description

This library defines parser combinators for precedence parsing.

Synopsis

Documentation

data ReadPrec a

Instances

Precedences

type Prec = Int

minPrec :: Prec

Precedence operations

lift :: ReadP a -> ReadPrec a

Lift a precedence-insensitive ReadP to a ReadPrec.

prec :: Prec -> ReadPrec a -> ReadPrec a

(prec n p) checks whether the precedence context is less than or equal to n, and

  • if not, fails
  • if so, parses p in context n.

step :: ReadPrec a -> ReadPrec a

Increases the precedence context by one.

reset :: ReadPrec a -> ReadPrec a

Resets the precedence context to zero.

Other operations

All are based directly on their similarly-named ReadP counterparts.

get :: ReadPrec Char

Consumes and returns the next character. Fails if there is no input left.

look :: ReadPrec String

Look-ahead: returns the part of the input that is left, without consuming it.

(+++) :: ReadPrec a -> ReadPrec a -> ReadPrec a

Symmetric choice.

(<++) :: ReadPrec a -> ReadPrec a -> ReadPrec a

Local, exclusive, left-biased choice: If left parser locally produces any result at all, then right parser is not used.

pfail :: ReadPrec a

Always fails.

choice :: [ReadPrec a] -> ReadPrec a

Combines all parsers in the specified list.

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