Safe Haskell	Safe
Language	Haskell98

Text.ParserCombinators.Poly.Lex

Contents

The Parser datatype
- Basic parsers
- Re-parsing
Re-export all more general combinators

Description

In a strict language, where creating the entire input list of tokens in one shot may be infeasible, we can use a lazy "callback" kind of architecture instead. The lexer returns a single token at a time, together with a continuation.

This module defines a Parser type (capable of use with the Poly combinators), specialised to the callback-lexer style of input stream.

Synopsis

data LexReturn t
- = LexReturn t String (String -> LexReturn t)
- | LexFinish
newtype Parser t a = P (LexReturn t -> Result (LexReturn t) a)
data Result z a
- = Success z a
- | Failure z String
- | Committed (Result z a)
runParser :: Parser t a -> LexReturn t -> (Either String a, String)
next :: Parser t t
eof :: Parser t ()
satisfy :: (t -> Bool) -> Parser t t
onFail :: Parser t a -> Parser t a -> Parser t a
reparse :: [t] -> Parser t ()
module Text.ParserCombinators.Poly.Base
module Control.Applicative

The Parser datatype

data LexReturn t Source #

In a strict language, where creating the entire input list of tokens in one shot may be infeasible, we can use a lazy "callback" kind of architecture instead. The lexer returns a single token at a time, together with a continuation. The next parser is responsible for pulling on the token stream, applying the continuation where necessary.

Constructors

LexReturn t String (String -> LexReturn t)
LexFinish

newtype Parser t a Source #

This Parser datatype is a specialised parsing monad with error reporting. This version is specialised to pre-lexed String input, where the lexer has been written to yield a LexReturn.

Constructors

P (LexReturn t -> Result (LexReturn t) a)

Instances

Monad (Parser t) Source #
Instance details Defined in Text.ParserCombinators.Poly.Lex Methods (>>=) :: Parser t a -> (a -> Parser t b) -> Parser t b # (>>) :: Parser t a -> Parser t b -> Parser t b # return :: a -> Parser t a # fail :: String -> Parser t a #
Functor (Parser t) Source #
Instance details Defined in Text.ParserCombinators.Poly.Lex Methods fmap :: (a -> b) -> Parser t a -> Parser t b # (<$) :: a -> Parser t b -> Parser t a #
MonadFail (Parser t) Source #
Instance details Defined in Text.ParserCombinators.Poly.Lex Methods fail :: String -> Parser t a #
Applicative (Parser t) Source #
Instance details Defined in Text.ParserCombinators.Poly.Lex Methods pure :: a -> Parser t a # (<>) :: Parser t (a -> b) -> Parser t a -> Parser t b # liftA2 :: (a -> b -> c) -> Parser t a -> Parser t b -> Parser t c # (>) :: Parser t a -> Parser t b -> Parser t b # (<*) :: Parser t a -> Parser t b -> Parser t a #
Alternative (Parser t) Source #
Instance details Defined in Text.ParserCombinators.Poly.Lex Methods empty :: Parser t a # (<\|>) :: Parser t a -> Parser t a -> Parser t a # some :: Parser t a -> Parser t [a] # many :: Parser t a -> Parser t [a] #
PolyParse (Parser t) Source #
Instance details Defined in Text.ParserCombinators.Poly.Lex
Commitment (Parser t) Source #
Instance details Defined in Text.ParserCombinators.Poly.Lex Methods commit :: Parser t a -> Parser t a Source # adjustErr :: Parser t a -> (String -> String) -> Parser t a Source # oneOf' :: [(String, Parser t a)] -> Parser t a Source #

data Result z a Source #

A return type like Either, that distinguishes not only between right and wrong answers, but also has commitment, so that a failure cannot be undone. This should only be used for writing very primitive parsers - really it is an internal detail of the library. The z type is the remaining unconsumed input.

Constructors

Success z a
Failure z String
Committed (Result z a)

Instances

Functor (Result z) Source #
Instance details Defined in Text.ParserCombinators.Poly.Result Methods fmap :: (a -> b) -> Result z a -> Result z b # (<$) :: a -> Result z b -> Result z a #

runParser :: Parser t a -> LexReturn t -> (Either String a, String) Source #

Apply a parser to an input token sequence.

Basic parsers

next :: Parser t t Source #

Simply return the next token in the input tokenstream.

eof :: Parser t () Source #

Succeed if the end of file/input has been reached, fail otherwise.

satisfy :: (t -> Bool) -> Parser t t Source #

Return the next token if it satisfies the given predicate.

onFail :: Parser t a -> Parser t a -> Parser t a infixl 6 Source #

p onFail q means parse p, unless p fails, in which case parse q instead. Can be chained together to give multiple attempts to parse something. (Note that q could itself be a failing parser, e.g. to change the error message from that defined in p to something different.) However, a severe failure in p cannot be ignored.

Re-parsing

reparse :: [t] -> Parser t () Source #

Push some tokens back onto the front of the input stream and reparse. This is useful e.g. for recursively expanding macros. When the user-parser recognises a macro use, it can lookup the macro expansion from the parse state, lex it, and then stuff the lexed expansion back down into the parser.

Re-export all more general combinators

module Text.ParserCombinators.Poly.Base

module Control.Applicative