org.scalactic

TraversableEqualityConstraints

trait TraversableEqualityConstraints extends SeqEqualityConstraints with SetEqualityConstraints with MapEqualityConstraints

Provides three implicit methods that loosen the equality constraint defined by TypeCheckedTripleEquals or ConversionCheckedTripleEquals for Scala Traversables to one that more closely matches Scala's approach to Traversable equality.

Scala's approach to Traversable equality is that if the objects being compared are ether both Seqs, both Sets, or both Maps, the elements are compared to determine equality. This means you could compare an immutable Vector and a mutable ListBuffer for equality, for instance, and get true so long as the two Seqs contained the same elements in the same order. Here's an example:

scala> import scala.collection.mutable.ListBuffer
import scala.collection.mutable.ListBuffer

scala> Vector(1, 2) == ListBuffer(1, 2)
res0: Boolean = true

Such a comparison would not, however, compile if you used === under either TypeCheckedTripleEquals or ConversionCheckedTripleEquals, because Vector and ListBuffer are not in a subtype/supertype relationship, nor does an implicit conversion by default exist between them:

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

scala> import TypeCheckedTripleEquals._
import TypeCheckedTripleEquals._

scala> Vector(1, 2) === ListBuffer(1, 2)
<console>:16: error: types scala.collection.immutable.Vector[Int] and
  scala.collection.mutable.ListBuffer[Int] do not adhere to the equality constraint selected for
  the === and !== operators; the missing implicit parameter is of type
  org.scalactic.EqualityConstraint[scala.collection.immutable.Vector[Int],
  scala.collection.mutable.ListBuffer[Int]]
              Vector(1, 2) === ListBuffer(1, 2)
                           ^

If you mix or import the implicit conversion provided by TraversableEqualityConstraint, however, the comparison will be allowed:

scala> import TraversableEqualityConstraints._
import TraversableEqualityConstraints._

scala> Vector(1, 2) === ListBuffer(1, 2)
res2: Boolean = true

The equality constraints provided by this trait require that left and right sides are both subclasses of either scala.collection.GenSeq, scala.collection.GenSet, or scala.collection.GenMap, and that an EqualityConstraint can be found for the element types for Seq and Set, or the key and value types for Maps. In the example above, both the Vector and ListBuffer are subclasses of scala.collection.GenSeq, and the regular TypeCheckedTripleEquals provides equality constraints for the element types, both of which are Int. By contrast, this trait would not allow a Vector[Int] to be compared against a ListBuffer[java.util.Date], because no equality constraint will exist between the element types Int and Date:

scala> import java.util.Date
import java.util.Date

scala> Vector(1, 2) === ListBuffer(new Date, new Date)
<console>:20: error: types scala.collection.immutable.Vector[Int] and
  scala.collection.mutable.ListBuffer[java.util.Date] do not adhere to the equality constraint selected for
  the === and !== operators; the missing implicit parameter is of type
  org.scalactic.EqualityConstraint[scala.collection.immutable.Vector[Int],
  scala.collection.mutable.ListBuffer[java.util.Date]]
              Vector(1, 2) === ListBuffer(new Date, new Date)
                           ^

This trait simply mixes together SeqEqualityConstraints, SetEqualityConstraints, and MapEqualityConstraints.

Source
TraversableEqualityConstraints.scala
Linear Supertypes
MapEqualityConstraints, SetEqualityConstraints, SeqEqualityConstraints, AnyRef, Any
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TraversableEqualityConstraints
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  1. TraversableEqualityConstraints
  2. MapEqualityConstraints
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  1. final def !=(arg0: Any): Boolean

    Definition Classes
    AnyRef → Any

  2. final def ##(): Int

    Definition Classes
    AnyRef → Any

  3. final def ==(arg0: Any): Boolean

    Definition Classes
    AnyRef → Any

  4. final def asInstanceOf[T0]: T0

    Definition Classes
    Any

  5. def clone(): AnyRef

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
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    @throws( ... )

  6. final def eq(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef

  7. def equals(arg0: Any): Boolean

    Definition Classes
    AnyRef → Any

  8. def finalize(): Unit

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )

  9. final def getClass(): Class[_]

    Definition Classes
    AnyRef → Any

  10. def hashCode(): Int

    Definition Classes
    AnyRef → Any

  11. final def isInstanceOf[T0]: Boolean

    Definition Classes
    Any

  12. implicit def mapEqualityConstraint[KA, VA, CA[ka, kb] <: GenMap[ka, kb], KB, VB, CB[kb, vb] <: GenMap[kb, vb]](implicit equalityOfA: Equality[CA[KA, VA]], evKey: Constraint[KA, KB], evValue: Constraint[VA, VB]): Constraint[CA[KA, VA], CB[KB, VB]]

    Provides an equality constraint that allows two subtypes of scala.collection.GenMaps to be compared for equality with === so long as an EqualityConstraint is available for both key types and both value types.

    Provides an equality constraint that allows two subtypes of scala.collection.GenMaps to be compared for equality with === so long as an EqualityConstraint is available for both key types and both value types.

    Definition Classes
    MapEqualityConstraints

  13. final def ne(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef

  14. final def notify(): Unit

    Definition Classes
    AnyRef

  15. final def notifyAll(): Unit

    Definition Classes
    AnyRef

  16. implicit def seqEqualityConstraint[EA, CA[ea] <: GenSeq[ea], EB, CB[eb] <: GenSeq[eb]](implicit equalityOfA: Equality[CA[EA]], ev: Constraint[EA, EB]): Constraint[CA[EA], CB[EB]]

    Provides an equality constraint that allows two subtypes of scala.collection.GenSeqs to be compared for equality with === so long as an EqualityConstraint is available for the element types.

    Provides an equality constraint that allows two subtypes of scala.collection.GenSeqs to be compared for equality with === so long as an EqualityConstraint is available for the element types.

    Definition Classes
    SeqEqualityConstraints

  17. implicit def setEqualityConstraint[EA, CA[ea] <: GenSet[ea], EB, CB[eb] <: GenSet[eb]](implicit equalityOfA: Equality[CA[EA]], ev: Constraint[EA, EB]): Constraint[CA[EA], CB[EB]]

    Provides an equality constraint that allows two subtypes of scala.collection.GenSets to be compared for equality with === so long as an EqualityConstraint is available for the element types.

    Provides an equality constraint that allows two subtypes of scala.collection.GenSets to be compared for equality with === so long as an EqualityConstraint is available for the element types.

    Definition Classes
    SetEqualityConstraints

  18. final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
    AnyRef

  19. def toString(): String

    Definition Classes
    AnyRef → Any

  20. final def wait(): Unit

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    @throws( ... )

  21. final def wait(arg0: Long, arg1: Int): Unit

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    @throws( ... )

  22. final def wait(arg0: Long): Unit

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