Agda.Syntax.Parser.Comments

This module defines the lex action to lex nested comments. As is well-known this cannot be done by regular expressions (which, incidently, is probably the reason why C-comments don't nest).

When scanning nested comments we simply keep track of the nesting level, counting up for open comments and down for close comments.

Documentation

keepComments :: LexPredicate

Should comment tokens be output?

keepCommentsM :: Parser Bool

Should comment tokens be output?

nestedComment :: LexAction Token

Manually lexing a block comment. Assumes an open comment has been lexed. In the end the comment is discarded and lexToken is called to lex a real token.

hole :: LexAction Token

Lex a hole ({! ... !}). Holes can be nested. Returns TokSymbol SymQuestionMark.

skipBlock :: String -> String -> LookAhead ()

Skip a block of text enclosed by the given open and close strings. Assumes the first open string has been consumed. Open-close pairs may be nested.