ScalaTest Scalactic - 具有公差的自定义双等式，包括 Double.NaN 大小写

Question

我正在尝试创建一个自定义匹配器，它将考虑 Double.NaN 并将对非 nan 值使用容差。

import org.scalactic.{Equality, TolerantNumerics}
import org.scalatest.Matchers

trait MoreMatchers extends Matchers {

  implicit def doubleEqWithNaNAndTol: Equality[Double] = new Equality[Double] {

    implicit val tolerance: Equality[Double] = TolerantNumerics.tolerantDoubleEquality(1e-6)

    def areEqual(expected: Double, actual: Any): Boolean = actual match {
      case number: Double if number.isNaN => expected.isNaN
      case _: Double => actual === expected
      case _ => false
    }

  }

很遗憾，它不起作用。

assert(0.00226685508536916 === 0.0022668550853691587)  // failure - doesn't use tolerance
assert (Double.NaN === Double.NaN )  // success

如果在断言中输入公差，则如果存在 NaN 则失败。

assert(0.00226685508536916 === 0.0022668550853691587 +- 1e-6)  // success
assert (Double.NaN === Double.NaN  +- 1e-6)  // failure - can't use tolerance when NaN

如果我像下面这样调用它，那么就可以了。

implicit val tolerance: Equality[Double] = TolerantNumerics.tolerantDoubleEquality(1e-6)

def eq(expected: Double, actual: Double): Boolean = expected match {
    case x if x.isNaN => actual.isNaN
    case _ => actual === expected
}

然后将其命名为：

assert(eq(...,...))

我想知道是否可以使用第一种方式让它工作。你以前遇到过这样的情况吗？你能提出任何解决方案吗？任何帮助将不胜感激:)

谢谢， ele

Answer 1

非常感谢 eirikr @d6 :)，请参阅 custom equality gist

中的解决方案

基本上，在上面的代码中，您需要在比较非 nan 双精度数时使用 tolerance.areEqual(expected, number)，以便能够使用该比较中隐含的公差。

import org.scalactic.{Equality, TolerantNumerics}
import org.scalatest.Matchers

trait MoreMatchers extends Matchers {

  implicit def doubleEqWithNaNAndTol: Equality[Double] = new Equality[Double] {

    implicit val tolerance: Equality[Double] = TolerantNumerics.tolerantDoubleEquality(1e-6)

    def areEqual(expected: Double, actual: Any): Boolean = actual match {
      case x: Double if x.isNaN => expected.isNaN
      case x: Double => tolerance.areEqual(expected, x)
      case _ => false
    }

  }

此致， ele

ScalaTest Scalactic - 具有公差的自定义双等式，包括 Double.NaN 大小写

ScalaTest Scalactic - Custom Double Equality with tolerance including Double.NaN case

scala

equality

nan

scalatest

scalactic