Default equality

Scalactic defines a default Equality that treats arrays specially. Its areEqual method works by first calling .deep on any passed array, then calling == on the resulting left-hand object, passing in the resulting right-hand object. If a more specific implicit Equality is not available for the left-hand type in an === or !== expression, default equality will be used.

Here are some examples showing the special treatment of arrays:

scala> import org.scalactic._
import org.scalactic._

scala> import TripleEquals._
import TripleEquals._

scala> Array(1, 2, 3) == Array(1, 2, 3)
res0: Boolean = false

scala> Array(1, 2, 3) === Array(1, 2, 3)
res1: Boolean = true

scala> Array(1, 2, 3) == List(1, 2, 3)
<console>:14: warning: comparing values of types Array[Int] and List[Int] using `==' will always yield false
              Array(1, 2, 3) == List(1, 2, 3)
                             ^
res2: Boolean = false

scala> Array(1, 2, 3) === List(1, 2, 3)
res3: Boolean = true

scala> List(1, 2, 3) == Array(1, 2, 3)
res4: Boolean = false

scala> List(1, 2, 3) === Array(1, 2, 3)
res5: Boolean = true

You can obtain a default equality via the default method of the Equality companion object, or from the defaultEquality method defined in TripleEqualsSupport.

Next, learn about Constrained equality.