如何在quickCheck中使用'oneof'（Haskell） [英] How to use 'oneof' in quickCheck (Haskell)

问题描述

然而，我不确定如何使用oneof -功能正常。你可以给我一些提示吗？

  prop_candidates :: Sudoku  - > Bool 
 prop_candidates su = isSudoku newSu&& isOkay newSu 
其中
 newSu =更新su aBlank aCandidate 
 aCandidate = oneof [return x | x<  - 候选suaBlank] 
 aBlank = oneof [return x | x<  - （blanks su）] 
  

以下是更多信息...

  type Pos =（Int，Int）
 update :: Sudoku  - > Pos  - >也许Int  - > Sudoku 
 blanks :: Sudoku  - > [Pos] 
个候选人:: Sudoku  - > Pos  - > [Int] 
 [return x | x<  - （空白例子）] ::（Monad m）=> [m Pos] 
  

现在我已经用这个道具拼了3个小时了，所以任何想法都是值得欢迎的！

解决方案

我在驾驶的是你有一种混淆。也就是说， aBlank 不是 Pos ，但是 Gen Pos ，所以更新su aBlank aCandidate 没有意义！事实上，你想要的是一种在初始数独时产生新的数独的方法;换句话说，一个函数

  similarSudoku :: Sudoku  - > Gen Sudoku 
  

现在我们可以编写它：

  similarSudoku su = do aBlank<  -  elements（blanks su）
  - 比oneOf简单[return x | x < -  blanks su] 
 aCandidate<  - 元素（候选项su aBlank）
返回（更新su aBlank aCandidate）
  

$ b

或者甚至更简单：

pre $类似的方法su = liftM2（更新su）（元素）（元素（候选人su aBlank））

该属性看起来像

  prop_similar :: Sudoku  - > Gen Bool 
 prop_similar su = do newSu < -  similarSudoku su 
 return（isSudoku newSu&& isOkay newSu）
  

因为有实例

 可测试Bool 
可测试的prop => Testable（Gen prop）
（Arbitrary a，Show a，Testable prop）=> Testable（a  - > prop）
  

Sudoku - > Gen Bool 也是 Testable （假设实例任意数独）。

I am trying to write a prop that changes a Sudoku and then checks if it's still valid.

However, I am not sure how to use the "oneof"-function properly. Can you give me some hints, please?

prop_candidates :: Sudoku -> Bool
prop_candidates su = isSudoku newSu && isOkay newSu
    where
        newSu       = update su aBlank aCandidate
        aCandidate  = oneof [return x | x <- candidates su aBlank]
        aBlank      = oneof [return x | x <- (blanks su)]

Here are some more info...

type Pos = (Int, Int)
update :: Sudoku -> Pos -> Maybe Int -> Sudoku
blanks :: Sudoku -> [Pos]
candidates :: Sudoku -> Pos -> [Int]
[return x | x <- (blanks example)] :: (Monad m) => [m Pos]

I have struggeled with this prop for 3 hours now, so any ideas are welcome!

解决方案

What I was driving at is that you have a type mix-up. Namely, aBlank is not a Pos, but a Gen Pos, so update su aBlank aCandidate makes no sense! In fact, what you want is a way to generate a new sudoku given an initial sudoku; in other words a function

similarSudoku :: Sudoku -> Gen Sudoku

Now we can write it:

similarSudoku su = do aBlank <- elements (blanks su) 
                      -- simpler than oneOf [return x | x <- blanks su]
                      aCandidate <- elements (candidates su aBlank)
                      return (update su aBlank aCandidate)

or even simpler:

similarSudoku su = liftM2 (update su) (elements (blanks su)) (elements (candidates su aBlank))

And the property looks like

prop_similar :: Sudoku -> Gen Bool
prop_similar su = do newSu <- similarSudoku su
                     return (isSudoku newSu && isOkay newSu)

Since there are instances

Testable Bool
Testable prop => Testable (Gen prop)
(Arbitrary a, Show a, Testable prop) => Testable (a -> prop)

Sudoku -> Gen Bool is Testable as well (assuming instance Arbitrary Sudoku).

这篇关于如何在quickCheck中使用'oneof'（Haskell）的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！