Question

HUnit是否有某种方式做出近似的平等？显然，这失败了：

test1 = TestCase (assertEqual "Should equal" (get_scores) [(0.3, 0.3), (0.6, 0.36), (1.0, 0.3399999)])

Answer 1

对于浮点近似比较，有一个带有一些很好的工具库的库：

http://hackage.haskell.org/package/ieee754

Answer 2

注意：我不知道是否有正确/官方/可接受的方式来执行此操作。

Here's assertEqual的源代码：

assertEqual :: (Eq a, Show a) => String -- ^ The message prefix 
                              -> a      -- ^ The expected value 
                              -> a      -- ^ The actual value
                              -> Assertion
assertEqual preface expected actual =
  unless (actual == expected) (assertFailure msg)
 where msg = (if null preface then "" else preface ++ "\n") ++
             "expected: " ++ show expected ++ "\n but got: " ++ show actual

基于此，在JUnit's function for testing double equality上，我们可以创建自己的风格：

import Control.Monad (unless)

assertEquals ::   String  -- ^ The message prefix
               -> Double  -- ^ The maximum difference between expected and actual
               -> Double  -- ^ The expected value
               -> Double  -- ^ The actual value
               -> Assertion
assertEquals preface delta expected actual = 
  unless (abs (expected - actual) < delta) (assertFailure msg)
 where msg = ... same as above ...

Answer 3

就我的目的而言，这个助手功能运作良好：

assertFloatEqual text a b = 
  assertEqual text (take 6 (show a)) (take 6 (show b))

Answer 4

我使我的数据类型与代码相等的实例使用2个小数位。以下是使用笛卡尔点的示例：

data Point =  Point { x_axis :: Double, y_axis :: Double, z_axis :: Double } 
              deriving (Show)

等于

的实例

为了避免双舍入误差和导致的三角错误由于微小的差异，同一点，因此CornerPoints为/=，给它一个.01的范围，并且仍然允许这些点相等。

axisEqual :: (Eq a, Num a, Ord a, Fractional a) => a -> a -> Bool

axisEqual  a b
  | (abs (a - b)) <= 0.011 = True
  | otherwise      = False

instance Eq Point where

  Point x y z == Point xa ya za
    | (axisEqual x xa) && (axisEqual y ya)  &&(axisEqual z za) = True 
    | otherwise = False

用HUnit测试双打上的haskell平等？

4 个答案:

等于