base-4.3.1.0: Basic libraries

Portability | non-portable (uses Text.ParserCombinators.ReadP)
Stability | provisional
Maintainer | libraries@haskell.org

Text.ParserCombinators.ReadPrec

Contents

- Precedences
- Precedence operations
- Other operations
- Converters

Description

This library defines parser combinators for precedence parsing.

Synopsis

- data ReadPrec a
- type Prec = Int
- minPrec :: Prec
- lift :: ReadP a -> ReadPrec a
- prec :: Prec -> ReadPrec a -> ReadPrec a
- step :: ReadPrec a -> ReadPrec a
- reset :: ReadPrec a -> ReadPrec a
- get :: ReadPrec Char
- look :: ReadPrec String
- (+++) :: ReadPrec a -> ReadPrec a -> ReadPrec a
- (<++) :: ReadPrec a -> ReadPrec a -> ReadPrec a
- pfail :: ReadPrec a
- choice :: [ReadPrec a] -> ReadPrec a
- 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

# Documentation

data ReadPrec a

Instances

Monad ReadPrec |
Functor ReadPrec |
MonadPlus ReadPrec |

# 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