How Recursion Works in Ruby Programming

A function that calls itself directly or indirectly is called a recursive function, and the corresponding function is referred to as a recursive function. Recursion makes the process easier and it definitely reduces the compilation time.

We will try to understand the concept of recursion in Ruby with the help of a very simple example.

Let's suppose we are given an array and we want to print the product of all the elements of the array, in order to do that, we have two choices, we can do it iteratively or we can do it recursively.

Example 1

Let's first do it iteratively. Consider the code shown below where the multiplication of each element is returned by the function.

# Iterative program to print multiplication of array elements

def iterativeMultiplication(arr)
   mul = 1
   arr.each do |num|
      mul *= num
   end
   puts mul
end
iterativeMultiplication([1, 2, 3, 4, 5])

Output

It will generate the following output −

120

Example 2

Now let's do it recursively. Consider the recursive code shown below.

# Recursive program to print multiplication of array elements
def recursiveMultiplication(arr)
   return 1 if arr.length == 0
   arr[0] * recursiveMultiplication(arr[1..-1])
end
puts recursiveMultiplication([1,2,3,4,5])

Output

It will generate the following output −

120

Example 3

Now let's explore one more example, which is a very famous recursive problem. The problem is to print the famous n^th Fibonacci number.

Consider the code shown below −

# print fibonacci nth number in ruby

def printFib( n )
   return n if ( 0..1 ).include? n
   ( printFib( n - 1 ) + printFib( n - 2 ) )
end

puts printFib( 5 )

Output

It will generate the following output −

5