ConversionCheckedTripleEquals
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.
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))
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.
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))
Class used via an implicit conversion to enable any two objects to be compared with
=== and !== with an Option[String] result and an enforced type constraint between
two object types.
Class used via an implicit conversion to enable any two objects to be compared with
=== and !== with an Option[String] 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))
The benefit of using assert(a === b) rather than assert(a == b) in ScalaTest code is
that a TestFailedException produced by the former will include the values of a and b
in its detail message.
Note: This class has "Legacy" in its name because its approach to error messages will eventually be replaced by macros. Once ScalaTest no longer supports Scala 2.9,
this class will be deprecated in favor of class Equalizer. Instead of obtaining nice error messages via the Option[String]
returned by the methods of this class, the error messages will be obtained by a macro. The "legacy" approach to good error messages will continue to be
used, however, until ScalaTest no longer supports Scala 2.9, since macros were introduced to Scala (in experimental form) in 2.10.
The primary constructor takes one object, left, whose type is being converted to Equalizer. The left
value may be a null reference, because this is allowed by Scala's == operator.
Class used via an implicit conversion to enable any two objects to be compared with
=== and !== with an Option[String] result and no enforced type constraint between
two object types.
Class used via an implicit conversion to enable any two objects to be compared with
=== and !== with an Option[String] 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))
The benefit of using assert(a === b) rather than assert(a == b) in ScalaTest code is
that a TestFailedException produced by the former will include the values of a and b
in its detail message.
Note: This class has "Legacy" in its name because its approach to error messages will eventually be replaced by macros. Once ScalaTest no longer supports Scala 2.9,
this class will be deprecated in favor of class Equalizer. Instead of obtaining nice error messages via the Option[String]
returned by the methods of this class, the error messages will be obtained by a macro. The "legacy" approach to good error messages will continue to be
used, however, until ScalaTest no longer supports Scala 2.9, since macros were introduced to Scala (in experimental form) in 2.10.
The primary constructor takes one object, left, whose type is being converted to Equalizer. The left
value may be a null reference, because this is allowed by Scala's == operator.
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.
the Spread[T] against which to compare the left-hand value
a TripleEqualsInvocationOnSpread wrapping the passed Spread[T] value, with
expectingEqual set to false.
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.
a null reference
a TripleEqualsInvocation wrapping the passed null value, with expectingEqual
set to false.
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.
the right-hand side value for an equality assertion
a TripleEqualsInvocation wrapping the passed right value, with expectingEqual
set to false.
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.
the Spread[T] against which to compare the left-hand value
a TripleEqualsInvocationOnSpread wrapping the passed Spread[T] value, with
expectingEqual set to true.
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.
a null reference
a TripleEqualsInvocation wrapping the passed null value, with expectingEqual
set to true.
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.
the right-hand side value for an equality assertion
a TripleEqualsInvocation wrapping the passed right value, with expectingEqual
set to true.
Provides a Constraint[A, B] class for any two types A and B, enforcing the type constraint that B is
implicitly convertible to A, given an implicit Equivalence[A].
Provides a Constraint[A, B] class 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
ConversionCheckedLegacyTripleEquals, and
overriden as non-implicit by the other subtraits in this package.
an Equivalence[A] type class to which the Constraint.areEqual method will delegate to determine equality.
an implicit conversion from B to A
a Constraint[A, B] whose areEqual method delegates to the areEquivalent method of
the passed Equivalence[A].
Provides a Constraint[A, 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 Constraint[A, 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
LowPriorityTypeCheckedLegacyConstraint (extended by
TypeCheckedLegacyTripleEquals), and
overriden as non-implicit by the other subtraits in this package.
an Equivalence[B] type class to which the Constraint.areEqual method
will delegate to determine equality.
evidence that A is a subype of B
a Constraint[A, B] whose areEqual method delegates to the
areEquivalent method of the passed Equivalence[B].
Provides a Constraint[A, B] class for any two types A and B, enforcing the type constraint that A is
implicitly convertible to B, given an explicit Equivalence[B].
Provides a Constraint[A, B] class 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
LowPriorityConversionCheckedLegacyConstraint (extended by
ConversionCheckedLegacyTripleEquals), and
overriden as non-implicit by the other subtraits in this package.
a Constraint[A, B] whose areEqual method delegates to the areEquivalent method of
the passed Equivalence[B].
Provides a Constraint[A, B] 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 a Constraint[A, B] 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
TypeCheckedLegacyTripleEquals, and
overriden as non-implicit by the other subtraits in this package.
evidence that B is a subype of A
a Constraint[A, B] whose areEqual method delegates to the areEquivalent method of
the passed Equivalence[A].
Provides a Constraint[A, B] class for any two types A and B, enforcing the type constraint that B is
implicitly convertible to A, given an explicit Equivalence[A].
Provides a Constraint[A, B] class 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
ConversionCheckedLegacyTripleEquals, and
overriden as non-implicit by the other subtraits in this package.
an Equivalence[A] type class to which the Constraint.areEqual method will delegate to determine equality.
a Constraint[A, B] whose areEqual method delegates to the areEquivalent method of
the passed Equivalence[A].
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 subtraits TypeCheckedTripleEquals and
ConversionCheckedTripleEquals, and overriden as
non-implicit by the other subtraits in this package.
the object whose type to convert to CheckingEqualizer.
if left is null.
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.
the object whose type to convert to Equalizer.
if left is null.
Converts to a LegacyCheckingEqualizer that provides === and !== operators
that result in Option[String] and enforce a type constraint.
Converts 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.
the object whose type to convert to LegacyCheckingEqualizer.
if left is null.
Converts to a LegacyEqualizer that provides === and !== operators that
result in Option[String] and enforce no type constraint.
Converts 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.
the object whose type to convert to LegacyEqualizer.
if left is null.
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 ==.
a default Equality for type A
Provides a Constraint[A, B] class for any two types A and B, enforcing the type constraint that A is
implicitly convertible to B, given an implicit Equivalence[B].
Provides a Constraint[A, B] class 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
LowPriorityConversionCheckedLegacyConstraint (extended by
ConversionCheckedLegacyTripleEquals), and
overriden as non-implicit by the other subtraits in this package.
an implicit conversion from A to B
a Constraint[A, B] whose areEqual method delegates to the areEquivalent method of
the passed Equivalence[B].
Provides a Constraint[A, 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 a Constraint[A, 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
LowPriorityTypeCheckedLegacyConstraint (extended by
TypeCheckedLegacyTripleEquals), and
overriden as non-implicit by the other subtraits in this package.
an Equivalence[B] type class to which the Constraint.areEqual method
will delegate to determine equality.
evidence that A is a subype of B
a Constraint[A, B] whose areEqual method delegates to the
areEquivalent method of the passed Equivalence[B].
Provides a Constraint[A, B] 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 a Constraint[A, B] 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
TypeCheckedLegacyTripleEquals, and
overriden as non-implicit by the other subtraits in this package.
evidence that B is a subype of A
a Constraint[A, B] whose areEqual method delegates to the areEquivalent method of
the passed Equivalence[A].
Provides a Constraint[A, B] class for any two types A and B, with no type constraint enforced, given an
implicit Equality[A].
Provides a Constraint[A, B] class 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
LegacyTripleEquals, and
overriden as non-implicit by the other subtraits in this package.
an Equality[A] type class to which the Constraint.areEqual method will delegate to determine equality.
a Constraint[A, B] whose areEqual method delegates to the areEqual method of
the passed Equality[A].
Provides
===and!==operators that returnBoolean, delegate the equality determination to anEqualitytype class, and require that either the types of the two values compared are in a subtype/supertype relationship, or that an implicit conversion is available that can convert from one type to the other.ConversionCheckedTripleEqualsis useful (in both production and test code) when you need determine equality for a type of object differently than itsequalsmethod—either you can't change theequalsmethod, or theequalsmethod is sensible generally, but you're in a special situation where you need something else—and/or you want a compile-time type check that allows types that are implicitly convertable in either (or both) directions.This trait is the middle ground of the three triple equals traits, in between
TripleEquals, the most lenient, andTypeCheckedTripleEquals, the most strict. IfTripleEqualsis mixed in or imported, the===can be used with any two types and still compile. IfTypeCheckedTripleEqualsis mixed in or imported, however, only types in a subtype or supertype relationship with each other (including when both types are exactly the same) will compile.ConversionCheckedTripleEqualsis slightly more accomodating, because in addition to compiling any use of===that will compile underTypeCheckedTripleEquals, it will also compile type types that would be rejected byTypeCheckedTripleEquals, so long as an implicit conversion (in either direction) from one type to another is available.For example, under
TypeCheckedTripleEquals, the following use of===will not compile, becauseIntandLongare not in a subtype/supertype relationship. (I.e.,Intis not a subtype or supertype ofLong):scala> import org.scalactic._ import org.scalactic._ scala> import TypeCheckedTripleEquals._ import TypeCheckedTripleEquals._ scala> 1 === 1L <console>:14: 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.scalactic.Constraint[Int,Long] 1 === 1L ^Trait
TypeCheckedTripleEqualsrejects typesIntandLongbecause they are not directly related via subtyping. However, an implicit widening conversion fromInttoLongdoes exist (imported implicitly fromscala.Predef), soConversionCheckedTripleEqualswill allow it:The implicit conversion can go in either direction: from the left type to the right type, or vice versa. In the above expression the implicit conversion goes from left to right (the
Inton the left to theLongon the right). It also works the other way:This trait will override or hide implicit methods defined by its sibling traits,
BecauseTripleEqualsorTypeCheckedTripleEquals, and can therefore be used to temporarily turn on or off conversion checking in a limited scope. Here's an example, in whichTypeCheckedTripleEqualswill cause a compiler error:IntandLongare not in a subtype/supertype relationship, comparing1and1Lin the context ofTypeCheckedTripleEqualswill 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.scalactic.Constraint[Int,Long] if (a === b) 0 // This line won't compile ^ one error foundYou can “relax” the type checking (i.e., by additionally allowing implicitly convertible types) locally by importing the members ofConversionCheckedTripleEqualsin a limited scope: With the above change, theExample.scalafile compiles fine. Conversion checking is enabled only inside the firstcmpmethod that takes anIntand aLong.TypeCheckedTripleEqualsis still enforcing its type constraint, for example, for thes === texpression in the other overloadedcmpmethod that takes strings. Because the methods inConversionCheckedTripleEquals(and its siblings) override all the methods defined in supertypeTripleEqualsSupport, 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. An alternative way to solve an unwanted compiler error caused by an over-zealous type constraint is with a widening type ascription. Here are some examples:scala> import org.scalactic._ import org.scalactic._ scala> import ConversionCheckedTripleEquals._ import ConversionCheckedTripleEquals._ scala> List(1, 2, 3) === Vector(1, 2, 3) <console>:14: error: types List[Int] and scala.collection.immutable.Vector[Int] do not adhere to the equality constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.Constraint[List[Int],scala.collection.immutable.Vector[Int]] List(1, 2, 3) === Vector(1, 2, 3) ^Although you could solve the above type error withTraversableEqualityConstraints, you could also simply widen the type of one side or the other toAny. BecauseAnyis a supertype of everything, the type constraint will be satisfied: You could alternatively widen a type to a more specific common supertype thanAny. For example, sinceList[Int]andVector[Int]are both subtypes ofSeq[Int], so you could widen either type toSeq[Int]to satisfy the type checker: