What is a recursive function?

Question

I’ve always heard that recursion is an intelligent idea that plays a central role in functional programming and computer science in general. From what I understand, briefly, there is recursion mutual and tail.

What is a recursive function? What are the main characteristics between mutual and tail recursiveness?

Answer 1

A recursive function is a function that calls itself.

They can be used to process a given operation and there are usually internal conditions for recursivities to be applied (since without conditions, it would call itself eternally, causing what we call an infinite loop).

For example, an excerpt from my library for lazy ajax loading by Angular (Javascript framework):

WMLaravelLazyLoad.prototype.untilCompleted = function () {

    var that = this;

    that.next().then(function () {
        that.untilCompleted();
    })
};

In the above example, when the action is completed, the function is called immediately, but until next() has some feedback that causes the code of then be triggered.

I had asked a question where the use of recursion is approached, which although it is a little different, you can have an idea of the advantage of using it.

Why do they say that recursive setTimeout is better than setInterval?

On the question about mutual and tail recursiveness, you can see:

What is the difference between recursion and tail recursion?

Answer 2

The function is recursive is a function that calls itself, always.

It is actually horrible, mainly for treatment and memory management.

EXAMPLE OF RECURSIVE FUNCTION

#include <stdio.h>

void movetorre (int n, char orig, char dest, char aux){
   if (n==1) {printf("\nMover disco 1 da torre %c para a torre %c", orig, dest);
   return;}
      movetorre(n-1,orig,aux,dest);
      printf("\nMover disco %d da torre %c para a torre %c", n, orig, dest);
      movetorre(n-1,aux,dest,orig);
};

int main(){
   int discos;
   printf("\t\t\t\tTORRE DE HANOY\n\n");
   printf("Digite a quantidade de discos: ");
   scanf("%d",&discos);
   movetorre(discos,'A','C','B');
   return 0;
}

This is a simple example of a recursive algorithm called the Hanoi tower, made in c.

You may notice that she calls herself.

MUTUAL RECURSION

Mutual recursion occurs when two or more functions are defined in terms of each other.

The most important basic example of a data type that can be defined by mutual recursion is a tree, which can be mutually defined recursively in terms of a forest (a list of trees).

TAIL RECURSION

Tail recursive functions form a subclass of recursive functions, in which the recursive call is the last instruction to be executed.