whitespace = discard (char ' ') <|>
             discard (char '\n') <|>
             discard (string "\r\n") <|>
             discard (char '\t')
whitespace = discard (char ' ') <|>
             discard (char '\n') <|>
             discard (string "\r\n") <|>
             discard (char '\t')
whitespace = discard (char ' ') <|>
             discard (char '\n') <|>
             discard (string "\r\n") <|>
             discard (char '\t')