#531: Text.Parsec.Combinators.notFollowedBy too restrictive ----------------------------+----------------------------------------------- Reporter: nzeh | Owner: Type: enhancement | Status: new Priority: normal | Milestone: _|_ Component: Cabal library | Version: 1.6.0.1 Severity: minor | Keywords: Difficulty: unknown | Ghcversion: Platform: | ----------------------------+----------------------------------------------- Say, you want to write something like {{{ aParser :: Parser String aParser = many1 $ noneOf "a" <|> ( char 'a' >> notFollowedBy $ string "rrgh" >> return 'a' ) }}} This fails because, according to the type signature of notFollowedBy, since the parser parses a stream characters, the parser given to notFollowedBy must have return type Char, which it doesn't. The same happens for something a little more meaningful such as {{{ nonFinalA :: Parser () nonFinalA = char 'a' >> notFollowedBy eof }}} because eof has return type (). This is a request to change the type signature of notFollowedBy to accept a parser with arbitrary return type. Rationale: * The return type is ignored anyway. * The return type has only a loose connection with what part of the input stream the parser consumes. -- Ticket URL: http://hackage.haskell.org/trac/hackage/ticket/531 Hackage http://haskell.org/cabal/ Hackage: Cabal and related projects