Agda-2.2.6: A dependently typed functional programming language and proof assistant Source code Contents Index

Agda.Syntax.Parser.Alex

Contents Alex requirements Lex actions Monad operations

Description

This module defines the things required by Alex and some other Alex related things.

Synopsis

data AlexInput = AlexInput { lexPos :: !Position lexInput :: String lexPrevChar :: !Char } alexInputPrevChar :: AlexInput -> Char alexGetChar :: AlexInput -> Maybe (Char, AlexInput) type LexAction r = PreviousInput -> CurrentInput -> TokenLength -> Parser r type LexPredicate = ([LexState], ParseFlags) -> PreviousInput -> TokenLength -> CurrentInput -> Bool (.&&.) :: LexPredicate -> LexPredicate -> LexPredicate (.||.) :: LexPredicate -> LexPredicate -> LexPredicate not' :: LexPredicate -> LexPredicate type PreviousInput = AlexInput type CurrentInput = AlexInput type TokenLength = Int getLexInput :: Parser AlexInput setLexInput :: AlexInput -> Parser ()

Alex requirements

data AlexInput Source

This is what the lexer manipulates. Constructors AlexInput lexPos :: !Position current position lexInput :: String current input lexPrevChar :: !Char previously read character

alexInputPrevChar :: AlexInput -> Char Source

Get the previously lexed character. Same as lexPrevChar. Alex needs this to be defined to handle "patterns with a left-context".

alexGetChar :: AlexInput -> Maybe (Char, AlexInput) Source

Lex a character. No surprises.

Lex actions

type LexAction r = PreviousInput -> CurrentInput -> TokenLength -> Parser r Source

In the lexer, regular expressions are associated with lex actions who's task it is to construct the tokens.

type LexPredicate = ([LexState], ParseFlags) -> PreviousInput -> TokenLength -> CurrentInput -> Bool Source

Sometimes regular expressions aren't enough. Alex provides a way to do arbitrary computations to see if the input matches. This is done with a lex predicate.

(.&&.) :: LexPredicate -> LexPredicate -> LexPredicate Source

Conjunction of LexPredicates.

(.||.) :: LexPredicate -> LexPredicate -> LexPredicate Source

Disjunction of LexPredicates.

not' :: LexPredicate -> LexPredicate Source

Negation of LexPredicates.

type PreviousInput = AlexInput Source

type CurrentInput = AlexInput Source

type TokenLength = Int Source

Monad operations

getLexInput :: Parser AlexInput Source

setLexInput :: AlexInput -> Parser () Source

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