Thanks. reservedOp is a better fit; ":+" should only be ":+". I also overcame my type issues in an ad-hoc manner, adding
return ()
whenever I needed to. -----Original Message----- From: Tillmann Rendel [mailto:rendel@rbg.informatik.tu-darmstadt.de] Sent: 30 March 2008 12:30 To: Paul Keir; haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] Parsec Expected Type Paul Keir wrote:
What I'd like is to parse either the string "parameter", or the string ":". I'm using 'reserved' and 'symbol' because they seem to correspond well to the concepts in the language I'm parsing.
You may consider using reservedOp for ":", depending on how ":+" should be parsed: for ":+" use reservedOp for ":" "+" use symbol If you use reserved, then ":name" will be parsed as ":name" not ":" "name" as you probably expect. generally, reserved is for identifier-like keywords, and reservedOp for operator-like keywords.
Perhaps I'd express my confusion better if I ask: Why are 'reserved' and 'symbol' different types?
I have no idea. They aren't in the Parsec manual on Daans site: http://legacy.cs.uu.nl/daan/download/parsec/parsec.html You can fix this by defining reserved name = ParsecToken.reserved tokenParser name >> return name instead of reserved = ParsecToken.reserved tokenParser to "import" the reserved component from the tokenParser to the toplevel. Now, reserved :: String -> CharParser st String Another option is to fix it the other way, by defining symbol name = ParsecToken.symbol tokenParser name >> return () or to fix it in a ad-hoc manner, by defining ignored = (>> return ()) and using it in the approbiate places, like parameterOrColon = reserved "parameter" <|> ignored (symbol ":") Tillmann