重载相等运算符的断言对于三等号失败但通过双重等号

Question

我重载了一个案例 class 的相等运算符：

case class Polygon(points: Seq[(Double, Double)]) extends Shape {
  def ==(that: Polygon): Boolean = { ... }
}

在断言中使用双等号时我的单元测试通过了：

import org.scalatest.FunSpec

class ShapeSpec extends FunSpec {
  describe("Polygon") {
    it("is equal to all its rotations") {
      val p = Polygon(Seq( ... ))
      for { i ← 0 until p.points.size } {
        val q = Polygon(p.points.drop(i) ++ p.points.take(i))
        assert(p == q)
      }
    }
  }
}

但是当使用 === 而不是 == 时，同样的测试失败了：

[info] Polygon
[info] - is equal to all its rotations *** FAILED ***
[info]   Polygon(List((-1.0,-1.0), (4.0,-1.0), (4.0,2.0), (1.0,2.0),
         (1.0,1.0), (-1.0,1.0))) did not equal PolygonM(List((4.0,-1.0),
         (4.0,2.0), (1.0,2.0), (1.0,1.0), (-1.0,1.0), (-1.0,-1.0)))
         (ShapeSpec.scala:28)

为什么会这样？

Answer 1

你拼错了。 ;)

应该是：

override def equals(x: Any): Boolean

重载相等运算符的断言对于三等号失败但通过双重等号

Assertion for overloaded equality operator fails for triple-equals but passes for double-equals

scala

scalatest

assertion

case-class