Partial Functions in Scala
Last Updated :
29 Mar, 2019
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Introduction:
When a function is not able to produce a return for every single variable input data given to it then that function is termed as Partial function. It can determine an output for a subset of some practicable inputs only. It can only be applied partially to the stated inputs.
Some important points:
Scala
- Partial functions are beneficent in understanding many inconsistent kind of Scala functions.
- It can be interpreted by utilizing case statements.
- It is a Trait, which needs two methods namely isDefinedAt and apply to be implemented.
// Scala program of
// Partial function
// Creating object
object Case
{
// Main method
def main(args: Array[String])
{
// Creating Partial function
// using two methods
val r = new PartialFunction[Int, Int]
{
// Applying isDefinedAt method
def isDefinedAt(q: Int) = q != 0
// Applying apply method
def apply(q: Int) = 12 * q
}
// Displays output if the
// condition is satisfied
println(r(10))
}
}
// Scala program of // Partial function// Creating object object Case{ // Main method def main(args: Array[String]) { // Creating Partial function // using two methods val r = new PartialFunction[Int, Int] { // Applying isDefinedAt method def isDefinedAt(q: Int) = q != 0 // Applying apply method def apply(q: Int) = 12 * q } // Displays output if the // condition is satisfied println(r(10)) }}
Output:
Here, two methods are defined for applying Partial function, where isDefinedAt states the condition and apply performs the operation if the given condition is satisfied.
Methods to define Partial functions:
There are some methods to define Partial function, which includes case statements, collect method, andThen, and orElse.
120
- Partial function using Case statement:
we will create a Partial function below using case statement.
Example:
Scala // Scala program using // case statements // Creating object object Case { // Main method def main(args: Array[String]) { // Creating Partial function val d: PartialFunction[Int, Int] = { // using case statement case x if (x % 3) == 0 => x * 3 } // Displays output if // the condition is // satisfied println(d(3)) } }
// Scala program using// case statements// Creating objectobject Case{// Main methoddef main(args: Array[String]){// Creating Partial functionval d: PartialFunction[Int, Int] ={// using case statementcase x if (x % 3) == 0 => x * 3}// Displays output if// the condition is// satisfiedprintln(d(3))}}Output:Here, Partial function is created using case statement so, apply and isDefinedAt is not required here.9
- Partial function using orElse:
This method is helpful in chaining Partial functions together.
Example:
Scala // Scala program using // orElse // Creating object object orElse { // Main method def main(args: Array[String]) { // Creating Partial function1 val M: PartialFunction[Int, Int] = { // using case statement case x if (x % 5) == 0 => x * 5 } // Creating Partial function2 val m: PartialFunction[Int, Int] = { // using case statement case y if (y % 2) == 0 => y * 2 } // chaining two partial // functions using orElse val r = M orElse m // Displays output for // which the given condition // is satisfied println(r(5)) println(r(4)) } }
// Scala program using// orElse// Creating objectobject orElse{// Main methoddef main(args: Array[String]){// Creating Partial function1val M: PartialFunction[Int, Int] ={// using case statementcase x if (x % 5) == 0 => x * 5}// Creating Partial function2val m: PartialFunction[Int, Int] ={// using case statementcase y if (y % 2) == 0 => y * 2}// chaining two partial// functions using orElseval r = M orElse m// Displays output for// which the given condition// is satisfiedprintln(r(5))println(r(4))}}Output:Here, orElse will return output for which the given condition is satisfied.25 8
- Partial function using Collect method:
Collect method requests Partial function to every single element of the collection and thus, helps in constructing a new collection.
Example:
Scala // Scala program using // collect method // Creating object object Collect { // Main method def main(args: Array[String]) { // Creating Partial function val M: PartialFunction[Int, Int] = { // using case statement case x if (x % 5) != 0 => x * 5 } // Applying collect method val y = List(7, 15, 9) collect { M } // Displays output for which // the given condition // is satisfied println(y) } }
// Scala program using// collect method// Creating objectobject Collect{// Main methoddef main(args: Array[String]){// Creating Partial functionval M: PartialFunction[Int, Int] ={// using case statementcase x if (x % 5) != 0 => x * 5}// Applying collect methodval y = List(7, 15, 9) collect { M }// Displays output for which// the given condition// is satisfiedprintln(y)}}Output:Here, Collect will apply Partial function to all the elements of the List and will return a new List on the basis of the conditions stated.List(35, 45)
- Partial function using andThen:
This method appends at the end of the chains, which is utilized to continue towards additional chains of Partial functions.
Example:
Scala // Scala program using // andThen method // Creating object object andThen { // Main method def main(args: Array[String]) { // Creating Partial function val M: PartialFunction[Int, Int] = { // using case statement case x if (x % 4) != 0 => x * 4 } // Creating another function val append = (x: Int) => x * 10 // Applying andThen method val y = M andThen append // Displays output after // appending the another // function given println(y(7)) } }
// Scala program using// andThen method// Creating objectobject andThen{// Main methoddef main(args: Array[String]){// Creating Partial functionval M: PartialFunction[Int, Int] ={// using case statementcase x if (x % 4) != 0 => x * 4}// Creating another functionval append = (x: Int) => x * 10// Applying andThen methodval y = M andThen append// Displays output after// appending the another// function givenprintln(y(7))}}Output:Here, andThen will append the output of Partial function with the another function given and then will return that value.280
