this post was submitted on 16 Dec 2023
32 points (97.1% liked)

Programming

17366 readers
172 users here now

Welcome to the main community in programming.dev! Feel free to post anything relating to programming here!

Cross posting is strongly encouraged in the instance. If you feel your post or another person's post makes sense in another community cross post into it.

Hope you enjoy the instance!

Rules

Rules

  • Follow the programming.dev instance rules
  • Keep content related to programming in some way
  • If you're posting long videos try to add in some form of tldr for those who don't want to watch videos

Wormhole

Follow the wormhole through a path of communities !webdev@programming.dev

founded 1 year ago
MODERATORS
snowe@programming.dev
Ategon@programming.dev
MaungaHikoi@lemmy.nz
32
Why does the for loop repeat in this recursion? (lemm.ee)
submitted 10 months ago by milon@lemm.ee to c/programming@programming.dev
30 comments fedilink hide all child comments
 

I used the debugger to examine this code but not understanding a couple areas.

  1. Why does the for loop repeat after it exits to print a new line? If it exits the loop, shouldn't it be done with it?
  2. Why is n incremented and not i as stated with i++?

int main(void)
{
    int height = get_int("Height: ");

    draw(height);
}

void draw(int n)
{
    if (n <= 0)
    {
        return;
    }

    draw(n - 1);

    for (int i = 0; i < n; i++)
    {
        printf("#");
    }
    printf("\n");
}
you are viewing a single comment's thread
view the rest of the comments
[–] abhibeckert@lemmy.world 1 points 10 months ago* (last edited 10 months ago)

Recursion is a little easier to understand if you use goto instead of functions. Functions are a high level concept in the C language (and most other languages) but it gets compiled down to (essentially) the older goto style of programming.

Most modern languages don't even have goto support, since functions are generally more reliable, however as a programmer you should be aware what's going on under the hood. Here's your code rewritten to use goto (I also generally rewrote the whole thing to be a bit easier to grok):

int main(void)
{
    int height = get_int("Height: ");
    int row = 1;
    int col = 0;

draw:
    if (row > height)
    {
        goto end;
    }

    if (col < row)
    {
        printf("#");
        col++;
        goto draw;
    }
    
    // Move to the next row
    printf("\n");
    row++;
    col = 0;
    goto draw;

end:
    return 0;
}