readFloat :: IO Float readFloat = fmap read getLine main :: IO () main = do putStr "输入第一个数字： " first <- readFloat putStr "输入第二个数字： " second <- readFloat putStrLn $ show first ++ " + " ++ show second ++ " = " ++ show ( first + second )
输入：
输入第一个数字： 9.5 输入第二个数字： -2.02
输出：
9.5 + -2.02 = 7.48