How to generate the nth Fibonacci number in Haskell

Overview

A Fibonacci sequence is one in which any integer is the sum of its two preceding numbers. It begins with 0 and 1 and goes up to infinity. Following is the Fibonacci sequence:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, … and so on.

Algorithm

The formula to compute the nth Fibonacci number is as follows:

Code

Following is the implementation of the formula above in Haskell:

Explanation

• Line 1: We define the condition F(0) = 0.
• Line 2: We define the condition F(1) = 1.
• Line 3: We implement the recursive expression of the algorithm. The name of the function is fib.
• Line 5: We invoke the fib function with n as 8.