On Sun, 2007-11-18 at 19:37 -0500, Berlin Brown wrote:

On Nov 18, 2007 7:32 PM, Berlin Brown wrote:

...

I am sure many of you have looked at the scheme in haskell example that is on the web by Jonathan Tang. If you are familiar with the code, I need a little help trying to add scheme style comments:

"; This is my comment"

The preferred way to do that is to use a token helper function: token :: P a -> P a token p = do r <- p whiteSpace return r -- or, if you add a Control.Applicative instance for your -- parser type, this is just: token p = p <* whiteSpace Then you handle comments as whitespace: whiteSpace :: P () whiteSpace = skipMany $ spaces <|> (char ';' >> skipMany (satisfy (/='\n'))) Then you just use that like this: symbol :: P String symbol = token $ many1 $ satisfy $ not . (`elem` "()[]; ") See also Parsec's TokenParser.

On Nov 22, 2007, at 0:50 , Berlin Brown wrote:

token :: Parser -> Parser String token p = do r <- p whiteSpace return $ String r

You have an indentation problem: whiteSpace and return should be at the level of "r", not "p". -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH