sealed abstract class AndThen[-T, +R] extends (T) => R with Product with Serializable
A function type of a single input that can do function composition
(via andThen and compose) in constant stack space with amortized
linear time application (in the number of constituent functions).
Example:
val seed = AndThen((x: Int) => x + 1) val f = (0 until 10000).foldLeft(seed)((acc, _) => acc.andThen(_ + 1)) // This should not trigger stack overflow ;-) f(0)
This can be used to build stack safe data structures that make
use of lambdas. The perfect candidates for usage with AndThen
are the data structures using a signature like this (where
F[_] is a monadic type):
A => F[B]As an example, if we described this data structure, the naive
solution for that map is stack unsafe:
case class Resource[F[_], A, B]( acquire: F[A], use: A => F[B], release: A => F[Unit]) { def flatMap[C](f: B => C)(implicit F: Functor[F]): Resource[F, A, C] = { Resource( ra.acquire, // Stack Unsafe! a => ra.use(a).map(f), ra.release) } }
To describe a flatMap operation for this data type, AndThen
can save the day:
def flatMap[C](f: B => C)(implicit F: Functor[F]): Resource[F, A, C] = { Resource( ra.acquire, AndThen(ra.use).andThen(_.map(f)), ra.release) }
- Source
- AndThen.scala
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- def andThen[A](g: (R) => A): AndThen[T, A]
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- final def apply(a: T): R
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- @throws(classOf[java.lang.CloneNotSupportedException]) @native()
- def compose[A](g: (A) => T): AndThen[A, R]
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- AndThen → Function1
- final def eq(arg0: AnyRef): Boolean
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- def productElementName(n: Int): String
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- def productElementNames: Iterator[String]
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- def productIterator: Iterator[Any]
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- def productPrefix: String
- Definition Classes
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- final def rotateAccum[E](_right: AndThen[R, E]): AndThen[T, E]
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