Packages

trait Defer[F[_]] extends Serializable

Defer is a type class that shows the ability to defer creation inside of the type constructor F[_].

This comes up with F[_] types that are implemented with a trampoline or are based on function application.

The law is that defer(fa) is equivalent to fa, but not evaluated immediately, so

scala> import cats._
scala> import cats.implicits._

scala> var evaluated = false
scala> val dfa = Defer[Eval].defer {
     |   evaluated = true
     |   Eval.now(21)
     | }

scala> evaluated
res0: Boolean = false

scala> Eq[Eval[Int]].eqv(dfa, Eval.now(21))
res1: Boolean = true
Source
Defer.scala
Linear Supertypes
Serializable, Serializable, AnyRef, Any
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  1. Defer
  2. Serializable
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Abstract Value Members

  1. abstract def defer[A](fa: ⇒ F[A]): F[A]

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 asInstanceOf[T0]: T0
    Definition Classes
    Any
  5. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  6. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  7. def equals(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  8. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  9. def fix[A](fn: (F[A]) ⇒ F[A]): F[A]

    Defer instances, like functions, parsers, generators, IO, etc...

    Defer instances, like functions, parsers, generators, IO, etc... often are used in recursive settings where this function is useful

    fix(fn) == fn(fix(fn))

    example:

    val parser: P[Int] = Defer[P].fix[Int] { rec => CharsIn("0123456789") | P("(") ~ rec ~ P(")") }

    Note, fn may not yield a terminating value in which case both of the above F[A] run forever.

  10. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  11. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  12. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  13. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  14. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  15. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  16. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  17. def toString(): String
    Definition Classes
    AnyRef → Any
  18. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  19. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  20. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()

Inherited from Serializable

Inherited from Serializable

Inherited from AnyRef

Inherited from Any

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