Packages

  • package root
    Definition Classes
    root
  • package cats

    The cats root package contains all the trait signatures of most Scala type classes.

    The cats root package contains all the trait signatures of most Scala type classes.

    Cats type classes are implemented using the approach from the Type classes as objects and implicits article.

    For each type class, cats provides three pieces: - Its signature: a trait that is polymorphic on a type parameter. Type class traits inherit from other type classes to indicate that any implementation of the lower type class (e.g. Applicative) can also serve as an instance for the higuer type class (e.g. Functor). - Type class 'instances, which are classes and objects that implement one or more type class signatures for some specific types. Type class instances for several data types from the Java or Scala standard libraries are declared in the subpackage cats.instances. - Syntax extensions, each of which provides the methods of the type class defines as extension methods (which in Scala 2 are encoded as implicit classes) for values of any type F; given that an instance of the type class for the receiver type (this) is in the implicit scope. Symtax extensions are declared in the cats.syntax package. - A set of laws, that are also generic on the type of the class, and are only defined on the operations of the type class. The purpose of these laws is to declare some algebraic relations (equations) between Scala expressions involving the operations of the type class, and test (but not verify) that implemented instances satisfy those equations. Laws are defined in the cats-laws package.

    Although most of cats type classes are declared in this package, some are declared in other packages: - type classes that operate on base types (kind *), and their implementations for standard library types, are contained in cats.kernel, which is a different SBT project. However, they are re-exported from this package. - type classes of kind F[_, _], such as cats.arrow.Profunctor" or cats.arrow.Arrow, which are relevant for Functional Reactive Programming or optics, are declared in the cats.arrow package. - Also, those type classes that abstract over (pure or impure) functional runtime effects are declared in the cats-effect library. - Some type classes for which no laws can be provided are left out of the main road, in a small and dirty alley. These are the alleycats.

    Definition Classes
    root
  • package evidence
    Definition Classes
    cats
  • As
  • AsInstances
  • Is
  • IsInstances

abstract class Is[A, B] extends Serializable

A value of A Is B is proof that the types A and B are the same. More powerfully, it asserts that they have the same meaning in all type contexts. This can be a more powerful assertion than A =:= B and is more easily used in manipulation of types while avoiding (potentially erroneous) coercions.

A Is B is also known as Leibniz equality.

Source
Is.scala
Linear Supertypes
Serializable, Serializable, AnyRef, Any
Type Hierarchy
Ordering
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Inherited
  1. Is
  2. Serializable
  3. Serializable
  4. AnyRef
  5. Any
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Visibility
  1. Public
  2. All

Instance Constructors

  1. new Is()

Abstract Value Members

  1. abstract def substitute[F[_]](fa: F[A]): F[B]

    To create an instance of A Is B you must show that for every choice of F[_] you can convert F[A] to F[B].

    To create an instance of A Is B you must show that for every choice of F[_] you can convert F[A] to F[B]. Loosely, this reads as saying that B must have the same effect as A in all contexts therefore allowing type substitution.

Concrete Value Members

  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 andThen[C](next: Is[B, C]): Is[A, C]

    Is is transitive and therefore values of Is can be composed in a chain much like functions.

    Is is transitive and therefore values of Is can be composed in a chain much like functions. See also compose.

    Annotations
    @inline()
  5. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  6. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native() @IntrinsicCandidate()
  7. final def coerce(a: A): B

    Substitution on identity brings about a direct coercion function of the same form that =:= provides.

    Substitution on identity brings about a direct coercion function of the same form that =:= provides.

    Annotations
    @inline()
  8. final def compose[C](prev: Is[C, A]): Is[C, B]

    Is is transitive and therefore values of Is can be composed in a chain much like functions.

    Is is transitive and therefore values of Is can be composed in a chain much like functions. See also andThen.

    Annotations
    @inline()
  9. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  10. def equals(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  11. final def flip: Is[B, A]

    Is is symmetric and therefore can be flipped around.

    Is is symmetric and therefore can be flipped around. Flipping is its own inverse, so x.flip.flip == x.

    Annotations
    @inline()
  12. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native() @IntrinsicCandidate()
  13. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native() @IntrinsicCandidate()
  14. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  15. final def lift[F[_]]: Is[F[A], F[B]]

    Sometimes for more complex substitutions it helps the typechecker to wrap one layer of F[_] context around the types you're equating before substitution.

    Sometimes for more complex substitutions it helps the typechecker to wrap one layer of F[_] context around the types you're equating before substitution.

    Annotations
    @inline()
  16. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  17. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native() @IntrinsicCandidate()
  18. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native() @IntrinsicCandidate()
  19. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  20. final def toPredef: =:=[A, B]

    A value A Is B is always sufficient to produce a similar Predef.=:= value.

    A value A Is B is always sufficient to produce a similar Predef.=:= value.

    Annotations
    @inline()
  21. def toString(): String
    Definition Classes
    AnyRef → Any
  22. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  23. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  24. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )

Deprecated Value Members

  1. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] ) @Deprecated
    Deprecated
  2. final def predefEq: =:=[A, B]

    A value A Is B is always sufficient to produce a similar Predef.=:= value.

    A value A Is B is always sufficient to produce a similar Predef.=:= value.

    Annotations
    @deprecated @inline()
    Deprecated

    (Since version 2.2.0) Use toPredef for consistency with As

Inherited from Serializable

Inherited from Serializable

Inherited from AnyRef

Inherited from Any

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