prefix :: String -> (a -> a) -> Operator Char () a
prefix symbol operation = Prefix (do { reservedOp symbol; 
                                       return operation })
prefix :: String -> (a -> a) -> Operator Char () a
prefix symbol operation = Prefix (do { reservedOp symbol; 
                                       return operation })
prefix symbol operation = Prefix (do { reservedOp symbol; 
                                       return operation })