partialfunctions.scala

partialfunctions.scala

// Full definition by defining the abstract methods
val pf1 = new PartialFunction[Int, Int]{
  def apply(x: Int): Int = x match { case t if isDefinedAt(t) => t + 1 }
  def isDefinedAt(x: Int): Boolean = x > 0 && x < 10
}                                         //> pf1  : PartialFunction[Int,Int] = <function1>
	
pf1.isDefinedAt(20)                       //> res0: Boolean = false
//pf1(20) //scala.MatchError
//pf1.apply(20) // same as above using aply method
	
pf1.isDefinedAt(9)                        //> res1: Boolean = true
pf1(9)                                    //> res2: Int = 10
	
// Same definition using case
val pf: PartialFunction[Int, Int] =
	{ case x if(x > 0 && x < 10) => x + 1 }  //> pf  : PartialFunction[Int,Int] = <function1>
	
pf.isDefinedAt(20)                        //> res3: Boolean = false
//pf(20)//scala.MatchError:
	
pf.isDefinedAt(9)                         //> res4: Boolean = true
pf(9)                                     //> res5: Int = 10

// Creates a regular functions that returns None if the function is not defined at the argument
val liftedPf1 = pf1 lift                  //> liftedPf1  : Int => Option[Int] = <function1>
	
liftedPf1(9)                              //> res6: Option[Int] = Some(10)
liftedPf1(20)                             //> res7: Option[Int] = None

// one regular function
val f = (x: Int) => x                     //> f  : Int => Int = <function1>

// Apply uses the partial functino if it is difined at the argument
pf1 applyOrElse (4, f)                    //> res6: Int = 5
// or the argument function otherwise
pf1 applyOrElse (30, f)                   //> res7: Int = 30