Agda.Syntax.Parser.Alex

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

Alex requirements

data AlexInput

This is what the lexer manipulates.

Constructors

AlexInput

Fields

• lexSrcFile :: !SrcFile

  File.

• lexPos :: !PositionWithoutFile

  Current position.

• lexInput :: String

  Current input.

• lexPrevChar :: !Char

  Previously read character.

lensLexInput :: Lens' String AlexInput

A lens for lexInput.

alexInputPrevChar :: AlexInput -> Char

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)

Lex a character. No surprises.

This function is used by Alex 2.

alexGetByte :: AlexInput -> Maybe (Word8, AlexInput)

A variant of alexGetChar.

This function is used by Alex 3.

Lex actions

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

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

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

Conjunction of LexPredicates.

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

Disjunction of LexPredicates.

not' :: LexPredicate -> LexPredicate

Negation of LexPredicates.

type PreviousInput = AlexInput

type CurrentInput = AlexInput

type TokenLength = Int

Monad operations

getLexInput :: Parser AlexInput

setLexInput :: AlexInput -> Parser ()