Question

这是我到目前为止所做的，我很确定函数本身是正确的，但我对main = do块中的操作感到困惑。我得到的错误是该函数想要一个整数但我给它一个字符串而不是。我假设它与getLine部分有关，而且我没有检查输入的数字是否为int。

factors :: Int -> [Int]
factors n = [x | x <- [1..n], mod n x == 0]
primeFactors :: Int -> [Int]
primeFactors n = [x | x <- [1..n], mod n x == 0, isPrime x]
isPrime x = (length (factors x)) == 2
main = do
  putStrLn "Enter a number."
  number <- getLine
  let x = factors number
  putStrLn x

运行此代码时出现的错误：

primeFactor.hs：9：19：错误：

    • Couldn't match type ‘[Char]’ with ‘Int’
      Expected type: Int
        Actual type: String
    • In the first argument of ‘factors’, namely ‘number’
      In the expression: factors number
      In an equation for ‘x’: x = factors number

primeFactor.hs：10：12：错误：

    • Couldn't match type ‘Int’ with ‘Char’
      Expected type: String
        Actual type: [Int]
    • In the first argument of ‘putStrLn’, namely ‘x’
      In a stmt of a 'do' block: putStrLn x
      In the expression:
        do { putStrLn "Enter a number.";
             number <- getLine;
             let x = factors number;
             putStrLn x }

Answer 1

let x = factors $ (read number :: Int)
print x

OR

number <- readLn

（感谢@Daniel）

这应该做的工作。

如何编写打印出指定数字的素因子的Haskell程序？

1 个答案: