Scalactic 3.2.17/org.scalactic/TripleEqualsSupport

TripleEqualsSupport

trait TripleEqualsSupport

Trait that defines abstract methods used to enforce compile-time type constraints for equality comparisons, and defines === and !== operators used by matchers.

The abstract methods of this trait are selectively implemented as implicit by subclasses to enable a spectrum of type constraints for the === and !== operators. As an illustration, if in the expression, a === b, the type of a is A and b is B, the following three levels of compile-time checking can be obtained from TripleEqualsSupport subtraits:

Unchecked - A and B can be any two types. This constraint level is available from subtrait TripleEquals.

Statically-checked - A must be a subtype of B, or vice versa, or must cooperate such that the equality laws stated in the equals contract are preserved. This (intermediate) constraint level is available by using subtrait TripleEquals and installing the SuperSafe Community Edition Scala compiler plugin.

Type-checked - A must be a subtype of B, or vice versa. (Both A and B can be the same type, because a type is considered a subtype of itself.) This (strongest) constraint level is available from subtrait TypeCheckedTripleEquals.

This trait defines all methods that need to be defined implicitly by the subtraits so that if multiple subtraits are used together, the inner-most subtrait in scope can not only enable the implicits it needs by overriding or hiding those methods (currently-in-scope as regular, non-implicit methods) and making them implicit, it can also disable any implicits enabled by its sibling subtraits in enclosing scopes. For example, if your test class mixes in TypeCheckedTripleEquals, inside your test class the following methods will be implicit:

  • convertToCheckingEqualizer

  • typeCheckedConstraint

  • lowPriorityTypeCheckedConstraint

  • convertEquivalenceToAToBConstraint

  • convertEquivalenceToBToAConstraint

If in the body of a test you want to turn off the type checking, you can import the members of TripleEquals in the body of that test. This will not only hide non-implicit methods convertToEqualizer unconstrainedEquality of TypeCheckedTripleEquals, replacing those with implicit ones defined in TripleEquals, it will also hide the three methods made implicit in TypeCheckedTripleEquals (and listed above), replacing them by non-implicit ones.

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.

Companion:
object
Source:
TripleEqualsSupport.scala
class Object
trait Matchable
class Any
object TripleEquals.type

Type members

Classlikes

class CheckingEqualizer[L](val leftSide: L)

Class used via an implicit conversion to enable two objects to be compared with === and !== with a Boolean result and an enforced type constraint between two object types. For example:

Class used via an implicit conversion to enable two objects to be compared with === and !== with a Boolean result and an enforced type constraint between two object types. For example:

assert(a === b)
assert(c !== d)

You can also check numeric values against another with a tolerance. Here are some examples:

assert(a === (2.0 +- 0.1))
assert(c !== (2.0 +- 0.1))
Value parameters:
leftSide

An object to convert to Equalizer, which represents the value on the left side of a === or !== invocation.

Source:
TripleEqualsSupport.scala
class Equalizer[L](val leftSide: L)

Class used via an implicit conversion to enable any two objects to be compared with === and !== with a Boolean result and no enforced type constraint between two object types. For example:

Class used via an implicit conversion to enable any two objects to be compared with === and !== with a Boolean result and no enforced type constraint between two object types. For example:

assert(a === b)
assert(c !== d)

You can also check numeric values against another with a tolerance. Here are some examples:

assert(a === (2.0 +- 0.1))
assert(c !== (2.0 +- 0.1))
Value parameters:
leftSide

An object to convert to Equalizer, which represents the value on the left side of a === or !== invocation.

Source:
TripleEqualsSupport.scala

Value members

Abstract methods

def convertEquivalenceToAToBConstraint[A, B](equivalenceOfB: Equivalence[B])(implicit ev: A <:< B): CanEqual[A, B]

Provides a A CanEqual B for any two types A and B, enforcing the type constraint that A must be a subtype of B, given an explicit Equivalence[B].

Provides a A CanEqual B for any two types A and B, enforcing the type constraint that A must be a subtype of B, given an explicit Equivalence[B].

This method is used to enable the Explicitly DSL for TypeCheckedTripleEquals by requiring an explicit Equivalance[B], but taking an implicit function that provides evidence that A is a subtype of B.

The returned Constraint's areEqual method uses the implicitly passed Equivalence[B]'s areEquivalent method to determine equality.

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

Value parameters:
equivalenceOfB

an Equivalence[B] type class to which the Constraint.areEqual method will delegate to determine equality.

ev

evidence that A is a subype of B

Returns:

an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].

Source:
TripleEqualsSupport.scala
def convertEquivalenceToBToAConstraint[A, B](equivalenceOfA: Equivalence[A])(implicit ev: B <:< A): CanEqual[A, B]

Provides an A CanEqual B instance for any two types A and B, enforcing the type constraint that B must be a subtype of A, given an explicit Equivalence[A].

Provides an A CanEqual B instance for any two types A and B, enforcing the type constraint that B must be a subtype of A, given an explicit Equivalence[A].

This method is used to enable the Explicitly DSL for TypeCheckedTripleEquals by requiring an explicit Equivalance[B], but taking an implicit function that provides evidence that A is a subtype of B. For example, under TypeCheckedTripleEquals, this method (as an implicit method), would be used to compile this statement:

def closeEnoughTo1(num: Double): Boolean =
 (num === 1.0)(decided by forgivingEquality)

The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.

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

Value parameters:
equalityOfA

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

ev

evidence that B is a subype of A

Returns:

an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].

Source:
TripleEqualsSupport.scala
def convertToCheckingEqualizer[T](left: T): CheckingEqualizer[T]

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

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

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

Value parameters:
left

the object whose type to convert to CheckingEqualizer.

Throws:
NullPointerException

if left is null.

Source:
TripleEqualsSupport.scala
def convertToEqualizer[T](left: T): Equalizer[T]

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

Converts 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.

Value parameters:
left

the object whose type to convert to Equalizer.

Throws:
NullPointerException

if left is null.

Source:
TripleEqualsSupport.scala
def lowPriorityTypeCheckedConstraint[A, B](implicit equivalenceOfB: Equivalence[B], ev: A <:< B): CanEqual[A, B]

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

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

The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.

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

Value parameters:
equivalenceOfB

an Equivalence[B] type class to which the Constraint.areEqual method will delegate to determine equality.

ev

evidence that A is a subype of B

Returns:

an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].

Source:
TripleEqualsSupport.scala
def typeCheckedConstraint[A, B](implicit equivalenceOfA: Equivalence[A], ev: B <:< A): CanEqual[A, B]

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

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

The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.

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

Value parameters:
equalityOfA

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

ev

evidence that B is a subype of A

Returns:

an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].

Source:
TripleEqualsSupport.scala
def unconstrainedEquality[A, B](implicit equalityOfA: Equality[A]): CanEqual[A, B]

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

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

The returned Constraint's areEqual method uses the implicitly passed Equality[A]'s areEqual method to determine equality.

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

Value parameters:
equalityOfA

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

Returns:

an A CanEqual B instance whose areEqual method delegates to the areEqual method of the passed Equality[A].

Source:
TripleEqualsSupport.scala

Concrete methods

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.

Value parameters:
right

the right-hand side value for an equality assertion

Returns:

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

Source:
TripleEqualsSupport.scala
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.

Value parameters:
right

a null reference

Returns:

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

Source:
TripleEqualsSupport.scala
def !==[T](right: Spread[T]): TripleEqualsInvocationOnSpread[T]

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

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

Value parameters:
right

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

Returns:

a TripleEqualsInvocationOnSpread wrapping the passed Spread[T] value, with expectingEqual set to false.

Source:
TripleEqualsSupport.scala
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.

Value parameters:
right

the right-hand side value for an equality assertion

Returns:

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

Source:
TripleEqualsSupport.scala
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.

Value parameters:
right

a null reference

Returns:

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

Source:
TripleEqualsSupport.scala
def ===[T](right: Spread[T]): TripleEqualsInvocationOnSpread[T]

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

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

Value parameters:
right

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

Returns:

a TripleEqualsInvocationOnSpread wrapping the passed Spread[T] value, with expectingEqual set to true.

Source:
TripleEqualsSupport.scala
def defaultEquality[A]: Equality[A]

Returns an Equality[A] for any type A that determines equality by first calling .deep on any Array (on either the left or right side), then comparing the resulting objects with ==.

Returns an Equality[A] for any type A that determines equality by first calling .deep on any Array (on either the left or right side), then comparing the resulting objects with ==.

Returns:

a default Equality for type A

Source:
TripleEqualsSupport.scala

Deprecated methods

@deprecated("The conversionCheckedConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.", "3.1.0")
def conversionCheckedConstraint[A, B](implicit equivalenceOfA: Equivalence[A], cnv: B => A): CanEqual[A, B]

The conversionCheckedConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.

The conversionCheckedConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.

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

The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.

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

Value parameters:
cnv

an implicit conversion from B to A

equivalenceOfA

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

Returns:

an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].

Deprecated
Source:
TripleEqualsSupport.scala
@deprecated("The convertEquivalenceToAToBConversionConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.", "3.1.0")
def convertEquivalenceToAToBConversionConstraint[A, B](equivalenceOfB: Equivalence[B])(implicit ev: A => B): CanEqual[A, B]

The convertEquivalenceToAToBConversionConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.

The convertEquivalenceToAToBConversionConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.

Provides an A CanEqual B instance for any two types A and B, enforcing the type constraint that A is implicitly convertible to B, given an explicit Equivalence[B].

This method is used to enable the Explicitly DSL for ConversionCheckedTripleEquals by requiring an explicit Equivalance[B], but taking an implicit function that converts from A to B.

The returned Constraint's areEqual method uses the implicitly passed Equivalence[B]'s areEquivalent method to determine equality.

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

Value parameters:
cnv

an implicit conversion from A to B

equalityOfB

an Equivalence[B] type class to which the Constraint.areEqual method will delegate to determine equality.

Returns:

an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].

Deprecated
Source:
TripleEqualsSupport.scala
@deprecated("The convertEquivalenceToBToAConversionConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.", "3.1.0")
def convertEquivalenceToBToAConversionConstraint[A, B](equivalenceOfA: Equivalence[A])(implicit ev: B => A): CanEqual[A, B]

The convertEquivalenceToBToAConversionConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.

The convertEquivalenceToBToAConversionConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.

Provides an A CanEqual B instance for any two types A and B, enforcing the type constraint that B is implicitly convertible to A, given an explicit Equivalence[A].

This method is used to enable the Explicitly DSL for ConversionCheckedTripleEquals by requiring an explicit Equivalance[A], but taking an implicit function that converts from B to A. For example, under ConversionCheckedTripleEquals, this method (as an implicit method), would be used to compile this statement:

def closeEnoughTo1(num: Double): Boolean =
 (num === 1.0)(decided by forgivingEquality)

The returned Constraint's areEqual method uses the implicitly passed Equivalence[A]'s areEquivalent method to determine equality.

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

Value parameters:
cnv

an implicit conversion from B to A

equivalenceOfA

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

Returns:

an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].

Deprecated
Source:
TripleEqualsSupport.scala
@deprecated("The lowPriorityConversionCheckedConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.", "3.1.0")
def lowPriorityConversionCheckedConstraint[A, B](implicit equivalenceOfB: Equivalence[B], cnv: A => B): CanEqual[A, B]

The lowPriorityConversionCheckedConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.

The lowPriorityConversionCheckedConstraint method has been deprecated and will be removed in a future version of Scalactic. It is no longer needed now that the deprecation period of ConversionCheckedTripleEquals has expired. It will not be replaced.

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

The returned Constraint's areEqual method uses the implicitly passed Equivalence[B]'s areEquivalent method to determine equality.

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

Value parameters:
cnv

an implicit conversion from A to B

equalityOfB

an Equivalence[B] type class to which the Constraint.areEqual method will delegate to determine equality.

Returns:

an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].

Deprecated
Source:
TripleEqualsSupport.scala