- | Parse whitespace.
--
-- > {s}?
--
-- Whitespace is 0 or 1 spaces, remembering that spaces have 1 or more
-- space characters.
w :: Parser String
w = (do x <- many s
        return $ concat x) 
    <?> "whitespace"

w :: Parser String
w = (do x <- many s
        return $ concat x) 
    <?> "whitespace"
w = (do x <- many s
        return $ concat x) 
    <?> "whitespace"