Creating multiple rectangles using SDL_Rect - c

Question

I'm creating a simulation for Conway's game of life using C and SDL. To represent the alive cells I would like to create multiple rectangles in the window which I have created. Is there any way to call SDL_Rect in a for loop without redefintion of SDL_Rect and output the result of the for loop all on the same renderer? Thank you.
My Code:
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>
#include <stdbool.h>
#include <SDL.h>
#define main SDL_main
#undef main
double CreateRectanglesX()
{
double x; double x_max = 640; double x_min = 20;
x = rand() / (x_max - x_min) / (double)RAND_MAX + x_min;
return x;
}
double CreateRectanglesY()
{
double y; double y_max = 480; double y_min = 20;
y = rand() / (y_max - y_min) / (double)RAND_MAX + y_min;
return y;
}
int main(int argc, char* argv[])
{
SDL_Init(SDL_INIT_VIDEO); //initializes the SDL/SDL2 window
SDL_Window *screen; //SDL window created with pointer
screen = SDL_CreateWindow("My Program Window", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, SDL_WINDOW_OPENGL);
//definition for pointer - dimensions of SDL window
SDL_Renderer *renderer; //Renderer created with pointer
renderer = SDL_CreateRenderer(screen, -1, SDL_RENDERER_ACCELERATED); //definition for pointer - still to learn
if (screen == NULL) //checks if window exists or not
{
printf("Could not create window: %s\n", SDL_GetError()); //returns error if window doesn't exsit
return 1;
}
SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255); //changes color of renderer
SDL_RenderClear(renderer);
SDL_RenderPresent(renderer); //displays the renderer with the changed color
for (int i = 0; i < 5; i++)
{
double x = CreateRectanglesX();
double y = CreateRectanglesY();
printf("%lf %lf", x, y);
SDL_Rect a;
a.x = x;
a.y = y;
a.w = 20;
a.h = 20;
SDL_SetRenderDrawColor(renderer, 0, 0, 255, 255);
SDL_RenderFillRect(renderer, &a);
SDL_RenderPresent(renderer);
}
SDL_Delay(5000); //wait time for window
SDL_DestroyWindow(screen);
SDL_QUIT;
return EXIT_SUCCESS;
}

Answer 1

The mistake was the fact that my random number generation formula with CreateRectanglesX() and CreateRectanglesY was wrong. It was
v = rand() / (x_max - x_min) / RAND_MAX + x_min;
Should have been:
v = rand() * (x_max - x_min) / RAND_MAX + x_min;
Only one rectangle was being displayed because the random numbers being produced with the random generation function were too close (due to wrong formula). Fixing the formula resolved the issue!