Recursive function in solidity?

Question

I need to call a recursive function with if statements. Is this possible in Solidity? Please provide an example.

Answer 1

It is possible to use recursive functions in Solidity. The following is a simple recursive function in solidity

pragma solidity ^0.5.12;

contract Test {
    uint x;
    function set(uint y) public {
        x = y;
    }

    function factorial(uint y) internal pure returns(uint){
        if (y == 1){
            return y;
        } else {
            return y * factorial(y-1);
        }
    }

    function get() public view returns(uint){
        return factorial(x);
    }
}

But please be aware that you should know what you are doing since recursive functions can end up costing huge gas and cause the transaction to revert atomically.

Answer 2

Fibonacci is perfect example to illustrate the recursion(tail):

Mathematically, the Fibonacci sequence is a recursive function that adds the previous elements to obtain the next element, Like below:

Fn = Fn-1 + Fn-2

---

function fib(uint n) public view returns(uint) { 
    if (n <= 1) {
       return n;
    } else {
       return this.fib(n - 1) + this.fib(n - 2);
    }
}

Note: Please avoid loops in your functions or actions that modify large areas of storage (this includes clearing or copying arrays in storage)