I am trying to make a rounding function

I am trying to make a rounding function that rounds to the nearest hundred, but when I tried it, it only outputs 0.

int roundrl() {
  rl = 200;
  if (rl < 100, rl > -1) {
    rl = 0;
  } else if (rl < 200, rl >99) {
    rl = 100;
  } else if (rl < 300, rl > 199) {
    rl = 200;
} else if (rl < 400, rl > 299) {
  rl = 300;
  } else if (rl < 500, rl > 399) {
    rl = 400;
  } else if (rl < 600, rl > 499) {
    rl = 500;
  } else if (rl < 700, rl > 599) {
    rl = 600;
  } else if (rl < 800, rl > 699) {
    rl = 700;
  } else if (rl < 900, rl > 799) {
    rl = 800;
  } else if (rl < 1000, rl > 899) {
    rl = 900;
  } else if (rl < 1100, rl > 999) {
    rl = 1000;
  }
}

What each else if is meant to do is to check if rl is below a number and above another.

there are line breaks, for some reason they didn't appear though

I doubt that that if structure is doing what you think. The comma does not belong in an if structure. Maybe && (logical and) is what you need there instead.

Try this with some different numbers:

int number = 450;

void setup()
{
   Serial.begin(115200);
   int tempNumber = number / 100;
   tempNumber = tempNumber * 100;
   Serial.println(tempNumber);
}

void loop()
{
}

Thanks for posting code properly on your first post. Few first time posters bother to read the guidelines. Good job.

You should use && instead of the comma.
The program should look like this

int roundrl(int rl) {
  if (rl < 100 && rl > -1) {
    rl = 0;
  } else if (rl < 200 && rl > 99) {
    rl = 100;
  } else if (rl < 300 && rl > 199) {
    rl = 200;
  }
  else if (rl < 400 && rl > 299) {
    rl = 300;
  } else if (rl < 500 && rl > 399) {
    rl = 400;
  } else if (rl < 600 && rl > 499) {
    rl = 500;
  } else if (rl < 700 && rl > 599) {
    rl = 600;
  } else if (rl < 800 && rl > 699) {
    rl = 700;
  } else if (rl < 900 && rl > 799) {
    rl = 800;
  } else if (rl < 1000 && rl > 899) {
    rl = 900;
  } else if (rl < 1100 && rl > 999) {
    rl = 1000;
  }
  return rl;
}

Thank you guys so much, when I first posted this it didn't show up as normal code for some reason, but now it is like that. That's why I put the reply there are line breaks there.

what about

#include <stdio.h>

int
main ()
{
    for (int i = 210; i < 300; i += 10)  {
        printf (" %6d %6d\n", i, 100 * ((i + 50) / 100) );
    }

    return 0;
}

which produces

    210    200
    220    200
    230    200
    240    200
    250    300
    260    300
    270    300
    280    300
    290    300