Scala - Recursive Function

A function which can call itself is known as recursive function. A recursive function generally ends with one or more boundary conditions which defines exit conditions from the function, otherwise it will go into an infinite loop.

Example: Factorial of a number

The factorial of a positive integer is the multiplication of all positive integer less than or equal to that number.

factorial of number n = n! = n(n-1)(n-2)...1

In the example below, a recursive function called factorial() is used to calculate factorial of a number.

object MainObject {
def factorial(x: Int) : Int = {
if(x == 0){
return 1
} else {
return x*factorial(x-1)
}
}

def main(args: Array[String]) {
println(s"3! = \${factorial(3)}")
println(s"5! = \${factorial(5)}")
println(s"10! = \${factorial(10)}")
}
}

The output of the above code will be:

3! =  6
5! =  120
10! =  3628800

Example: Fibonacci Sequence

Fibonacci terms are generally represented as Fn. A Fibonacci term is the sum of two previous terms and starts with 0 and 1. Mathematically, it can be represented as:

Fn = Fn-1 + Fn-2

With boundary conditions: F0 = 0 and F1 = 1

The Fibonacci Sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233...

In the example below, a recursive function called fib() is created to find out the nth term of Fibonacci sequence.

object MainObject {
def fib(n: Int) : Int = {
if(n == 0){
return 0
} else if (n == 1) {
return 1
} else {
return fib(n-1) + fib(n-2)
}
}

def main(args: Array[String]) {
println(s"Fibonacci 5th term: \${fib(5)}")
println(s"Fibonacci 6th term: \${fib(6)}")
println(s"Fibonacci 7th term: \${fib(7)}")
}
}

The above code will give the following output:

Fibonacci 5th term: 5
Fibonacci 6th term: 8
Fibonacci 7th term: 13

❮ Scala - Functions

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