org.scalautils

TripleEquals

trait TripleEquals extends EqualityConstraints

Provides === and !== operators that return Boolean, delegate the equality determination to an Equality type class, and require no relationship between the types of the two values compared.

Recommended Usage: Trait TripleEquals is useful (in both production and test code) when you need determine equality for a type of object differently than its equals method: either you can't change the equals method, or the equals method is sensible generally, but you are in a special situation where you need something else. If you also want a compile-time type check, however, you should use one of TripleEquals sibling traits: ConversionCheckedTripleEquals or TypeCheckedTripleEquals.

This trait will override or hide implicit methods defined by its sibling traits, ConversionCheckedTripleEquals or TypeCheckedTripleEquals, and can therefore be used to temporarily turn of type checking in a limited scope. Here's an example, in which TypeCheckedTripleEquals will cause a compiler error:

import org.scalautils._
import TypeCheckedTripleEquals._

object Example {

def cmp(a: Int, b: Long): Int = { if (a === b) 0 // This line won't compile else if (a < b) -1 else 1 }

def cmp(s: String, t: String): Int = { if (s === t) 0 else if (s < t) -1 else 1 } }

Because Int and Long are not in a subtype/supertype relationship, comparing 1 and 1L in the context of TypeCheckedTripleEquals will generate a compiler error:

Example.scala:9: error: types Int and Long do not adhere to the equality constraint selected for
the === and !== operators; they must either be in a subtype/supertype relationship, or, if
ConversionCheckedTripleEquals is in force, implicitly convertible in one direction or the other;
the missing implicit parameter is of type org.scalautils.EqualityConstraint[Int,Long]
    if (a === b) 0      // This line won't compile
          ^
one error found

You can “turn off” the type checking locally by importing the members of TripleEquals in a limited scope:

package org.scalautils.examples.tripleequals

import org.scalautils._
import TypeCheckedTripleEquals._

object Example {

  def cmp(a: Int, b: Long): Int = {
    import TripleEquals._
    if (a === b) 0
    else if (a < b) -1
    else 1
  }

 def cmp(s: String, t: String): Int = {
   if (s === t) 0
   else if (s < t) -1
   else 1
 }
}

With the above change, the Example.scala file compiles fine. Type checking is turned off only inside the first cmp method that takes an Int and a Long. TypeCheckedTripleEquals is still enforcing its type constraint, for example, for the s === t expression in the other overloaded cmp method that takes strings.

Because the methods in TripleEquals (and its siblings)override all the methods defined in supertype EqualityConstraints, you can achieve the same kind of nested tuning of equality constraints whether you mix in traits, import from companion objects, or use some combination of both.

In short, you should be able to select a primary constraint level via either a mixin or import, then change that in nested scopes however you want, again either through a mixin or import, without getting any implicit conversion ambiguity. The innermost constraint level in scope will always be in force.

Linear Supertypes
EqualityConstraints, AnyRef, Any
Known Subclasses
Ordering
  1. Alphabetic
  2. By inheritance
Inherited
  1. Hide All
  2. Show all
  1. TripleEquals
  2. EqualityConstraints
  3. AnyRef
  4. Any
Visibility
  1. Public
  2. All

Value Members

  1. def != (arg0: AnyRef): Boolean

    Attributes
    final
    Definition Classes
    AnyRef
  2. def != (arg0: Any): Boolean

    Attributes
    final
    Definition Classes
    Any
  3. def !== [T] (right: Interval[T]): TripleEqualsInvocationOnInterval[T]

    Returns a TripleEqualsInvocationOnInterval[T], given an Interval[T], to facilitate the “<left> should !== (<pivot> +- <tolerance>)” syntax of Matchers.

    Returns a TripleEqualsInvocationOnInterval[T], given an Interval[T], to facilitate the “<left> should !== (<pivot> +- <tolerance>)” syntax of Matchers.

    right

    the Interval[T] against which to compare the left-hand value

    returns

    a TripleEqualsInvocationOnInterval wrapping the passed Interval[T] value, with expectingEqual set to false.

    Definition Classes
    EqualityConstraints
  4. def !== (right: Null): TripleEqualsInvocation[Null]

    Returns a TripleEqualsInvocation[Null], given a null reference, to facilitate the “<left> should !== null” syntax of Matchers.

    Returns a TripleEqualsInvocation[Null], given a null reference, to facilitate the “<left> should !== null” syntax of Matchers.

    right

    a null reference

    returns

    a TripleEqualsInvocation wrapping the passed null value, with expectingEqual set to false.

    Definition Classes
    EqualityConstraints
  5. def !== [T] (right: T): TripleEqualsInvocation[T]

    Returns a TripleEqualsInvocation[T], given an object of type T, to facilitate the “<left> should !== <right>” syntax of Matchers.

    Returns a TripleEqualsInvocation[T], given an object of type T, to facilitate the “<left> should !== <right>” syntax of Matchers.

    right

    the right-hand side value for an equality assertion

    returns

    a TripleEqualsInvocation wrapping the passed right value, with expectingEqual set to false.

    Definition Classes
    EqualityConstraints
  6. def ## (): Int

    Attributes
    final
    Definition Classes
    AnyRef → Any
  7. def == (arg0: AnyRef): Boolean

    Attributes
    final
    Definition Classes
    AnyRef
  8. def == (arg0: Any): Boolean

    Attributes
    final
    Definition Classes
    Any
  9. def === [T] (right: Interval[T]): TripleEqualsInvocationOnInterval[T]

    Returns a TripleEqualsInvocationOnInterval[T], given an Interval[T], to facilitate the “<left> should === (<pivot> +- <tolerance>)” syntax of Matchers.

    Returns a TripleEqualsInvocationOnInterval[T], given an Interval[T], to facilitate the “<left> should === (<pivot> +- <tolerance>)” syntax of Matchers.

    right

    the Interval[T] against which to compare the left-hand value

    returns

    a TripleEqualsInvocationOnInterval wrapping the passed Interval[T] value, with expectingEqual set to true.

    Definition Classes
    EqualityConstraints
  10. def === (right: Null): TripleEqualsInvocation[Null]

    Returns a TripleEqualsInvocation[Null], given a null reference, to facilitate the “<left> should === null” syntax of Matchers.

    Returns a TripleEqualsInvocation[Null], given a null reference, to facilitate the “<left> should === null” syntax of Matchers.

    right

    a null reference

    returns

    a TripleEqualsInvocation wrapping the passed null value, with expectingEqual set to true.

    Definition Classes
    EqualityConstraints
  11. def === [T] (right: T): TripleEqualsInvocation[T]

    Returns a TripleEqualsInvocation[T], given an object of type T, to facilitate the “<left> should === <right>” syntax of Matchers.

    Returns a TripleEqualsInvocation[T], given an object of type T, to facilitate the “<left> should === <right>” syntax of Matchers.

    right

    the right-hand side value for an equality assertion

    returns

    a TripleEqualsInvocation wrapping the passed right value, with expectingEqual set to true.

    Definition Classes
    EqualityConstraints
  12. def asInstanceOf [T0] : T0

    Attributes
    final
    Definition Classes
    Any
  13. def clone (): AnyRef

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()
  14. def conversionCheckedEqualityConstraint [A, B] (implicit equalityOfA: Equality[A], cnv: (B) ⇒ A): EqualityConstraint[A, B]

    Provides an EqualityConstraint[A, B] class for any two types A and B, enforcing the type constraint that B is implicitly convertible to A, given an implicit Equality[A].

    Provides an EqualityConstraint[A, B] class for any two types A and B, enforcing the type constraint that B is implicitly convertible to A, given an implicit Equality[A].

    The implicitly passed Equality[A] must be used to determine equality by the returned EqualityConstraint's areEqual method.

    This method is overridden and made implicit by subtraits ConversionCheckedTripleEquals) and ConversionCheckedLegacyTripleEquals, and overriden as non-implicit by the other subtraits in this package.

    equalityOfA

    an Equality[A] type class to which the EqualityConstraint.areEqual method will delegate to determine equality.

    cnv

    an implicit conversion from B to A

    returns

    an EqualityConstraint[A, B] whose areEqual method delegates to the areEqual method of the passed Equality[A].

    Definition Classes
    TripleEqualsEqualityConstraints
  15. def convertToCheckingEqualizer [T] (left: T): CheckingEqualizer[T]

    Convert to an CheckingEqualizer that provides === and !== operators that result in Boolean and enforce a type constraint.

    Convert to an CheckingEqualizer that provides === and !== operators that result in Boolean and enforce a type constraint.

    This method is overridden and made implicit by subtraits TypeCheckedTripleEquals and ConversionCheckedTripleEquals, and overriden as non-implicit by the other subtraits in this package.

    left

    the object whose type to convert to CheckingEqualizer.

    Definition Classes
    TripleEqualsEqualityConstraints
  16. implicit def convertToEqualizer [T] (left: T): Equalizer[T]

    Convert to an Equalizer that provides === and !== operators that result in Boolean and enforce no type constraint.

    Convert to an Equalizer that provides === and !== operators that result in Boolean and enforce no type constraint.

    This method is overridden and made implicit by subtrait TripleEquals and overriden as non-implicit by the other subtraits in this package.

    left

    the object whose type to convert to Equalizer.

    Attributes
    implicit
    Definition Classes
    TripleEqualsEqualityConstraints
  17. def convertToLegacyCheckingEqualizer [T] (left: T): LegacyCheckingEqualizer[T]

    Convert to a LegacyCheckingEqualizer that provides === and !== operators that result in Option[String] and enforce a type constraint.

    Convert to a LegacyCheckingEqualizer that provides === and !== operators that result in Option[String] and enforce a type constraint.

    This method is overridden and made implicit by subtraits TypeCheckedLegacyTripleEquals and ConversionCheckedLegacyTripleEquals, and overriden as non-implicit by the other subtraits in this package.

    left

    the object whose type to convert to LegacyCheckingEqualizer.

    Definition Classes
    TripleEqualsEqualityConstraints
  18. def convertToLegacyEqualizer [T] (left: T): LegacyEqualizer[T]

    Convert to a LegacyEqualizer that provides === and !== operators that result in Option[String] and enforce no type constraint.

    Convert to a LegacyEqualizer that provides === and !== operators that result in Option[String] and enforce no type constraint.

    This method is overridden and made implicit by subtrait LegacyTripleEquals and overriden as non-implicit by the other subtraits in this package.

    left

    the object whose type to convert to LegacyEqualizer.

    Definition Classes
    TripleEqualsEqualityConstraints
  19. implicit def defaultEquality [A] : Equality[A]

    Return an Equality[A] for any type A that determines equality via the == operator on type A.

    Return an Equality[A] for any type A that determines equality via the == operator on type A.

    returns

    a DefaultEquality for type A

    Attributes
    implicit
    Definition Classes
    TripleEqualsEqualityConstraints
  20. def eq (arg0: AnyRef): Boolean

    Attributes
    final
    Definition Classes
    AnyRef
  21. def equals (arg0: Any): Boolean

    Definition Classes
    AnyRef → Any
  22. def finalize (): Unit

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()
  23. def getClass (): java.lang.Class[_]

    Attributes
    final
    Definition Classes
    AnyRef → Any
  24. def hashCode (): Int

    Definition Classes
    AnyRef → Any
  25. def isInstanceOf [T0] : Boolean

    Attributes
    final
    Definition Classes
    Any
  26. def lowPriorityConversionCheckedEqualityConstraint [A, B] (implicit equalityOfB: Equality[B], cnv: (A) ⇒ B): EqualityConstraint[A, B]

    Provides an EqualityConstraint[A, B] class for any two types A and B, enforcing the type constraint that A is implicitly convertible to B, given an implicit Equality[A].

    Provides an EqualityConstraint[A, B] class for any two types A and B, enforcing the type constraint that A is implicitly convertible to B, given an implicit Equality[A].

    The implicitly passed Equality[A] must be used to determine equality by the returned EqualityConstraint's areEqual method.

    This method is overridden and made implicit by subtraits LowPriorityConversionCheckedConstraint (extended by ConversionCheckedTripleEquals), and LowPriorityConversionCheckedLegacyConstraint (extended by ConversionCheckedLegacyTripleEquals), and overriden as non-implicit by the other subtraits in this package.

    cnv

    an implicit conversion from A to B

    returns

    an EqualityConstraint[A, B] whose areEqual method delegates to the areEqual method of the passed Equality[A].

    Definition Classes
    TripleEqualsEqualityConstraints
  27. def lowPriorityTypeCheckedEqualityConstraint [A, B] (implicit equalityOfA: Equality[A], ev: <:<[A, B]): EqualityConstraint[A, B]

    Provides an EqualityConstraint[A, B] class for any two types A and B, enforcing the type constraint that A must be a subtype of B, given an implicit Equality[A].

    Provides an EqualityConstraint[A, B] class for any two types A and B, enforcing the type constraint that A must be a subtype of B, given an implicit Equality[A].

    The implicitly passed Equality[A] must be used to determine equality by the returned EqualityConstraint's areEqual method.

    This method is overridden and made implicit by subtraits LowPriorityTypeCheckedConstraint (extended by TypeCheckedTripleEquals), and LowPriorityTypeCheckedLegacyConstraint (extended by TypeCheckedLegacyTripleEquals), and overriden as non-implicit by the other subtraits in this package.

    equalityOfA

    an Equality[A] type class to which the EqualityConstraint.areEqual method will delegate to determine equality.

    ev

    evidence that A is a subype of B

    returns

    an EqualityConstraint[A, B] whose areEqual method delegates to the areEqual method of the passed Equality[A].

    Definition Classes
    TripleEqualsEqualityConstraints
  28. def ne (arg0: AnyRef): Boolean

    Attributes
    final
    Definition Classes
    AnyRef
  29. def notify (): Unit

    Attributes
    final
    Definition Classes
    AnyRef
  30. def notifyAll (): Unit

    Attributes
    final
    Definition Classes
    AnyRef
  31. def synchronized [T0] (arg0: ⇒ T0): T0

    Attributes
    final
    Definition Classes
    AnyRef
  32. def toString (): String

    Definition Classes
    AnyRef → Any
  33. def typeCheckedEqualityConstraint [A, B] (implicit equalityOfA: Equality[A], ev: <:<[B, A]): EqualityConstraint[A, B]

    Provides an EqualityConstraint[A, B] class for any two types A and B, enforcing the type constraint that B must be a subtype of A, given an implicit Equality[A].

    Provides an EqualityConstraint[A, B] class for any two types A and B, enforcing the type constraint that B must be a subtype of A, given an implicit Equality[A].

    The implicitly passed Equality[A] must be used to determine equality by the returned EqualityConstraint's areEqual method.

    This method is overridden and made implicit by subtraits TypeCheckedTripleEquals) and TypeCheckedLegacyTripleEquals, and overriden as non-implicit by the other subtraits in this package.

    equalityOfA

    an Equality[A] type class to which the EqualityConstraint.areEqual method will delegate to determine equality.

    ev

    evidence that B is a subype of A

    returns

    an EqualityConstraint[A, B] whose areEqual method delegates to the areEqual method of the passed Equality[A].

    Definition Classes
    TripleEqualsEqualityConstraints
  34. implicit def unconstrainedEquality [A, B] (implicit equalityOfA: Equality[A]): EqualityConstraint[A, B]

    Provides an EqualityConstraint[A, B] class for any two types A and B, with no type constraint enforced, given an implicit Equality[A].

    Provides an EqualityConstraint[A, B] class for any two types A and B, with no type constraint enforced, given an implicit Equality[A].

    The implicitly passed Equality[A] must be used to determine equality by the returned EqualityConstraint's areEqual method.

    This method is overridden and made implicit by subtraits TripleEquals and LegacyTripleEquals, and overriden as non-implicit by the other subtraits in this package.

    equalityOfA

    an Equality[A] type class to which the EqualityConstraint.areEqual method will delegate to determine equality.

    returns

    an EqualityConstraint[A, B] whose areEqual method delegates to the areEqual method of the passed Equality[A].

    Attributes
    implicit
    Definition Classes
    TripleEqualsEqualityConstraints
  35. def wait (): Unit

    Attributes
    final
    Definition Classes
    AnyRef
    Annotations
    @throws()
  36. def wait (arg0: Long, arg1: Int): Unit

    Attributes
    final
    Definition Classes
    AnyRef
    Annotations
    @throws()
  37. def wait (arg0: Long): Unit

    Attributes
    final
    Definition Classes
    AnyRef
    Annotations
    @throws()

Inherited from EqualityConstraints

Inherited from AnyRef

Inherited from Any