scala.PartialFunction.scala Maven / Gradle / Ivy
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2002-2009, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala
/** A partial function of type PartialFunction[A, B] is a
* unary function where the domain does not include all values of type
* A. The function isDefinedAt allows to
* test dynamically, if a value is in the domain of the function.
*
* @author Martin Odersky
* @version 1.0, 16/07/2003
*/
trait PartialFunction[-A, +B] extends AnyRef with (A => B) {
/** Checks if a value is contained in the functions domain.
*
* @param x the value to test
* @return true, iff x is in the domain of this function.
*/
def isDefinedAt(x: A): Boolean
def orElse[A1 <: A, B1 >: B](that: PartialFunction[A1, B1]) : PartialFunction[A1, B1] =
new PartialFunction[A1, B1] {
def isDefinedAt(x: A1): Boolean =
PartialFunction.this.isDefinedAt(x) || that.isDefinedAt(x)
def apply(x: A1): B1 =
if (PartialFunction.this.isDefinedAt(x)) PartialFunction.this.apply(x)
else that.apply(x)
}
override def andThen[C](k: B => C) : PartialFunction[A, C] = new PartialFunction[A, C] {
def isDefinedAt(x: A): Boolean = PartialFunction.this.isDefinedAt(x)
def apply(x: A): C = k(PartialFunction.this.apply(x))
}
}