[英]Testing haskell equality on Doubles with HUnit?
Does HUnit have some way of doing approximate equalities? HUnit 有什么方法可以做近似等式吗? Clearly, this fails:
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)])
For floating point approximate comparison, there's a library with some nice utils: 对于浮点近似比较,有一个带有一些不错的工具的库:
http://hackage.haskell.org/package/ieee754 http://hackage.haskell.org/package/ieee754
Since this question was first asked, the HUnit-approx
package has been released.自从第一次提出这个问题以来,
HUnit-approx
软件包已经发布。
It uses an implicit variable, epsilon
, and an approximate equality operator, ~?~
, instead of ~=?
它使用隐式变量
epsilon
和近似相等运算符~?~
代替~=?
. .
A short example:一个简短的例子:
tweak :: Float -> Float
tweak x = x * 1.0001
egApproxTest = let ?epsilon = 0.01 in
[ "strictEqual" ~: 0 ~=? tweak 0,
"approxEqual" ~: 2 ~?~ tweak 2 ]
Note: I don't know if there's a correct/official/accepted way to do this. 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 the source code for assertEqual
: 这是
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
Based on that and on JUnit's function for testing double equality , we could create our own in the same style: 基于此以及基于JUnit的用于测试双重相等的功能 ,我们可以使用相同的样式创建自己的样式:
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 ...
For my purposes, this helper function worked well enough: 就我的目的而言,此辅助功能运行良好:
assertFloatEqual text a b =
assertEqual text (take 6 (show a)) (take 6 (show b))
I made my data type an instance of equal with code there to use 2 decimal places. 我将数据类型设置为等于代码的实例,以使用2个小数位。 Here is an example using a cartesian point:
这是使用笛卡尔点的示例:
data Point = Point { x_axis :: Double, y_axis :: Double, z_axis :: Double }
deriving (Show)
In order to avoid double rounding errors and trig errors which cause the same point, and thus CornerPoints, to be /=
due to tiny differences, give it a range of .01
, and still allow the points to be equal. 为了避免由于相同的微小差异而导致导致相同点(因此,CornerPoints)为
/=
两次舍入误差和触发误差,请将其范围设置为.01
,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
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