如何使用 Scalatest Equality 类型比较 Double 列表？

Question

这是我到目前为止尝试过的方法：

implicit val doubleEq = TolerantNumerics.tolerantDoubleEquality(0.1)

implicit val listEq = new Equivalence[List[Double]] {
  override def areEquivalent(a: List[Double], b: List[Double]): Boolean = {
    (a, b) match {
      case (Nil, Nil) => true
      case (x :: xs, y :: ys) => x === y && areEquivalent(xs, ys)
      case _ => false
    }
  }
}

第一个断言成功但第二个断言失败：

assert(1.0 === 1.01)

assert(List(1.0) === List(1.01))

有没有办法让集合也使用我为其元素定义的隐式？

Answer 1

在我的例子中，我通过提供 new Equality[List[Double]] 重新定义了 areEqual 方法，它是 Equivalence[List[Double]] 的子类，考虑到 areEqual 将 Any 作为第二个类型参数。

implicit val listEq = new Equality[List[Double]] {
  def areEqual(a: List[Double], b: Any): Boolean = {
    def areEqualRec(a: List[Double], b: List[Double]): Boolean = {
      (a, b) match {
        case (Nil, Nil) => true
        case (x :: xs, y :: ys) => x === y && areEquivalent(xs, ys)
        case _ => false
      }
    }
    b match {
      case daList: List[Double] => areEqualRec(a, daList)
      case _ => false
    }
  }
}

Answer 2

Equality classes 仅在导入时使用 TypeCheckedTripleEquals:

Provides === and !== operators that return Boolean, delegate the equality determination to an Equality type class, and require the types of the two values compared to be in a subtype/supertype relationship.

这是基础测试class我用来解决这个问题：

import org.scalactic.{Equivalence, TolerantNumerics, TypeCheckedTripleEquals}
import org.scalatest.FunSuite

abstract class UnitSpec extends FunSuite with TypeCheckedTripleEquals {
  implicit val doubleEq = TolerantNumerics.tolerantDoubleEquality(0.001)

  implicit val listEq = new Equivalence[List[Double]] {
    override def areEquivalent(a: List[Double], b: List[Double]): Boolean = {
      (a, b) match {
        case (Nil, Nil) => true
        case (x :: xs, y :: ys) => x === y && areEquivalent(xs, ys)
        case _ => false
      }
    }
  }
}

如何使用 Scalatest Equality 类型比较 Double 列表？

How to compare lists of Double using Scalatest Equality type?

scala

scalatest