booleanUnaryOp :: (LispVal -> Bool) -> [LispVal] -> ThrowsError LispVal
booleanUnaryOp op [arg] = return $ Bool $ op arg
booleanUnaryOp :: (LispVal -> Bool) -> [LispVal] -> ThrowsError LispVal
booleanUnaryOp op [arg] = return $ Bool $ op arg
booleanUnaryOp op [arg] = return $ Bool $ op arg