Scalactic 3.3.0-alpha.1/org.scalactic/TripleEquals

TripleEquals

org.scalactic.TripleEquals

See theTripleEquals companion object

trait TripleEquals extends TripleEqualsSupport

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. You can use the SuperSafe Community Edition compiler plugin to get a compile-time safety check of types being compared with ===. In situations where you need a stricter type check, you can use TypeCheckedTripleEquals.

This trait will override or hide implicit methods defined by its sibling trait, 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.scalactic._
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;
the missing implicit parameter is of type org.scalactic.Constraint[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.scalactic.examples.tripleequals

import org.scalactic._
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 TripleEqualsSupport, 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.

Attributes

Companion: object
Source: TripleEquals.scala
Graph
Supertypes: trait TripleEqualsSupport

class Object

trait Matchable

class Any
Known subtypes: object TripleEquals.type

Members list

Type members

Inherited classlikes

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.

Attributes

Inherited from:: TripleEqualsSupport
Source: TripleEqualsSupport.scala
Supertypes: class Object

trait Matchable

class Any

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.

Attributes

Inherited from:: TripleEqualsSupport
Source: TripleEqualsSupport.scala
Supertypes: class Object

trait Matchable

class Any

Value members

Concrete methods

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].

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

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].
Definition Classes: TripleEqualsSupport
Source: TripleEquals.scala

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

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].
Definition Classes: TripleEqualsSupport
Source: TripleEquals.scala

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.

Attributes

Throws: NullPointerException
if left is null.
Definition Classes: TripleEqualsSupport
Source: TripleEquals.scala

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.

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

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].
Definition Classes: TripleEqualsSupport
Source: TripleEquals.scala

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

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].
Definition Classes: TripleEqualsSupport
Source: TripleEquals.scala

Deprecated methods

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.

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].
Deprecated: true
Definition Classes: TripleEqualsSupport
Source: TripleEquals.scala

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.

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].
Deprecated: true
Definition Classes: TripleEqualsSupport
Source: TripleEquals.scala

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.

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[A].
Deprecated: true
Definition Classes: TripleEqualsSupport
Source: TripleEquals.scala

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.

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.

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEquivalent method of the passed Equivalence[B].
Deprecated: true
Definition Classes: TripleEqualsSupport
Source: TripleEquals.scala

Inherited methods

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

Attributes

Returns: a TripleEqualsInvocationOnSpread wrapping the passed Spread[T] value, with expectingEqual set to false.
Inherited from:: TripleEqualsSupport
Source: TripleEqualsSupport.scala

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

Value parameters

right: a null reference

Attributes

Returns: a TripleEqualsInvocation wrapping the passed null value, with expectingEqual set to false.
Inherited from:: TripleEqualsSupport
Source: TripleEqualsSupport.scala

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

Attributes

Returns: a TripleEqualsInvocation wrapping the passed right value, with expectingEqual set to false.
Inherited from:: TripleEqualsSupport
Source: TripleEqualsSupport.scala

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

Attributes

Returns: a TripleEqualsInvocationOnSpread wrapping the passed Spread[T] value, with expectingEqual set to true.
Inherited from:: TripleEqualsSupport
Source: TripleEqualsSupport.scala

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

Value parameters

right: a null reference

Attributes

Returns: a TripleEqualsInvocation wrapping the passed null value, with expectingEqual set to true.
Inherited from:: TripleEqualsSupport
Source: TripleEqualsSupport.scala

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

Attributes

Returns: a TripleEqualsInvocation wrapping the passed right value, with expectingEqual set to true.
Inherited from:: TripleEqualsSupport
Source: TripleEqualsSupport.scala

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 ==.

Attributes

Returns: a default Equality for type A
Inherited from:: TripleEqualsSupport
Source: TripleEqualsSupport.scala

Implicits

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.

Attributes

Throws: NullPointerException
if left is null.
Definition Classes: TripleEqualsSupport
Source: TripleEquals.scala

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.

Attributes

Returns: an A CanEqual B instance whose areEqual method delegates to the areEqual method of the passed Equality[A].
Definition Classes: TripleEqualsSupport
Source: TripleEquals.scala

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