Agda-2.5.1.2: A dependently typed functional programming language and proof assistant

Agda.Syntax.Parser.LexActions

Description

This module contains the building blocks used to construct the lexer.

Synopsis

# Main function

Scan the input to find the next token. Calls alexScanUser. This is the main lexing function where all the work happens. The function lexer, used by the parser is the continuation version of this function.

# Lex actions

## General actions

token :: (String -> Parser tok) -> LexAction tok Source #

The most general way of parsing a token.

withInterval :: ((Interval, String) -> tok) -> LexAction tok Source #

Parse a token from an Interval and the lexed string.

withInterval' :: (String -> a) -> ((Interval, a) -> tok) -> LexAction tok Source #

Like withInterval, but applies a function to the string.

withInterval_ :: (Interval -> r) -> LexAction r Source #

Return a token without looking at the lexed string.

Executed for layout keywords. Enters the layout state and performs the given action.

Enter a new state without consuming any input.

Exit the current state without consuming any input

Exit the current state and perform the given action.

Enter a new state throwing away the current lexeme.

Exit the current state throwing away the current lexeme.

For lexical errors we want to report the current position as the site of the error, whereas for parse errors the previous position is the one we're interested in (since this will be the position of the token we just lexed). This function does parseErrorAt the current position.

## Specialized actions

Parse a Keyword token, triggers layout for layoutKeywords.

Parse a Symbol token.

Parse an identifier. Identifiers can be qualified (see Name). Example: Foo.Bar.f

literal :: Read a => (Range -> a -> Literal) -> LexAction Token Source #

Parse a literal.

# Lex predicates

True when the given character is the next character of the input string.

True if we are at the end of the file.

True if the given state appears somewhere on the state stack