game of life / langdon's ant code i wrote to help someone learning first year C

gol_ant.c

#include <stdio.h>
#include <unistd.h>

#define NUM_ROWS 50
#define NUM_COLS 50


int wrap(int i, int max) {
    return ((i) % max + max) % max;
}
int row_wrap(int i) {
    return wrap(i,NUM_ROWS);
}
int col_wrap(int j) {
    return wrap(j,NUM_COLS);
}

void copy(int from[NUM_ROWS][NUM_COLS], int to[NUM_ROWS][NUM_COLS])
{
    for(int i = 0; i < NUM_ROWS; ++i) {
        for(int j = 0; j < NUM_COLS; ++j) {
            to[i][j] = from[i][j];
        }
    }
}
void swap(int g1[NUM_ROWS][NUM_COLS], int g2[NUM_ROWS][NUM_COLS])
{
    for(int i = 0; i < NUM_ROWS; ++i) {
        for(int j = 0; j < NUM_COLS; ++j) {
            int tmp = g1[i][j];
            g1[i][j] = g2[i][j];
            g2[i][j] = tmp;
        }
    }
}

void clear(int g[NUM_ROWS][NUM_COLS])
{
    for(int i = 0; i < NUM_ROWS; ++i) {
        for(int j = 0; j < NUM_COLS; ++j) {
            g[i][j] = 0;
        }
    }
}

void print(int g[NUM_ROWS][NUM_COLS])
{
    for(int j = 0; j < NUM_COLS; ++j) {
        printf("=");
    }
    printf("\n");
    for(int i = 0; i < NUM_ROWS; ++i) {
        for(int j = 0; j < NUM_COLS; ++j) {
            if(g[i][j] != 0) {
                printf("o");
            } else {
                printf(".");
            }
        }
        printf("\n");
    }
    for(int j = 0; j < NUM_COLS; ++j) {
        printf("=");
    }
    printf("\n\n");
}


int alive_neighbors(int grid[NUM_ROWS][NUM_COLS], int i, int j)
{
    int alive = 0;
    for(int l = -1; l < 2; ++l) {
        for(int m = -1; m < 2; ++m) {
            if((l != 0) || (m != 0)) {
                int ri = wrap(i+l,NUM_ROWS);
                int rj = wrap(j+m,NUM_COLS);
                if(grid[ri][rj] != 0) {
                    alive++;
                }
            }
        }
    }

    return alive;
}

void gol_step(int grid[NUM_ROWS][NUM_COLS])
{
    int tmpgrid[NUM_ROWS][NUM_COLS];
    copy(grid,tmpgrid);
    clear(grid);

    for(int i = 0; i < NUM_ROWS; ++i) {
        for(int j = 0; j < NUM_COLS; ++j) {
            int alive_nbrs = alive_neighbors(tmpgrid,i,j);
            int alive = tmpgrid[i][j];
            

            if(alive != 0) {
                if(alive_nbrs < 2 || alive_nbrs > 3) {
                    alive = 0;
                } else {
                    alive = 1;
                }
            }  else {
                if(alive_nbrs == 3) {
                    alive = 1;
                }
            }

            grid[i][j] = alive;
        }
    }
    
}

void set(int grid[NUM_ROWS][NUM_COLS], int i, int j, int val)
{
    int ri = wrap(i,NUM_ROWS);
    int rj = wrap(j,NUM_COLS);
    grid[ri][rj] = val;
}

void toad(int grid[NUM_ROWS][NUM_COLS], int i, int j)
{
    set(grid,i+0,j+0,1);
    set(grid,i+0,j+1,1);
    set(grid,i+0,j+2,1);
    set(grid,i+1,j+1,1);
    set(grid,i+1,j+2,1);
    set(grid,i+1,j+3,1);
}
void glider(int grid[NUM_ROWS][NUM_COLS], int i, int j)
{
    set(grid,i+0,j+1,1);
    set(grid,i+1,j+0,1);
    set(grid,i+2,j+0,1);
    set(grid,i+2,j+1,1);
    set(grid,i+2,j+2,1);
}
void beacon(int grid[NUM_ROWS][NUM_COLS], int i, int j)
{
    set(grid,i+0,j+0,1);
    set(grid,i+1,j+0,1);
    set(grid,i+0,j+1,1);
    set(grid,i+1,j+1,1);
    set(grid,i+2,j+2,1);
    set(grid,i+3,j+2,1);
    set(grid,i+2,j+3,1);
    set(grid,i+3,j+3,1);
}




int value(int grid[NUM_ROWS][NUM_COLS], int i, int j) {
    return grid[row_wrap(i)][row_wrap(j)];
}

//0 = north
//1 = east
//2 = south 
//3 = west 

int left(int dir) {
    return wrap(dir-1,4);
}
int right(int dir) {
    return wrap(dir+1,4);
}
int xoff(int dir) {
    switch(dir) {
        case 0: return 0;
        case 1: return 1;
        case 2: return 0;
        case 3: return -1;
    }
    return 0;
}
int yoff(int dir) {
    switch(dir) {
        case 0: return 1;
        case 1: return 0;
        case 2: return -1;
        case 3: return 0;
    }
    return 0;
}

void langdon_ant_step(int grid[NUM_ROWS][NUM_COLS], int* x_ptr, int* y_ptr, int* dir_ptr)
{
    int x = *x_ptr;
    int y = *y_ptr;
    int dir = *dir_ptr;
    if(value(grid,x,y) == 0) {//black
        dir = right(dir);
    } else {
        dir = left(dir);
    }

    grid[x][y] = grid[x][y]==0?1:0;

    x = row_wrap(x + xoff(dir));
    y = col_wrap(y + yoff(dir));

    *x_ptr = x;
    *y_ptr = y;
    *dir_ptr = dir;

}



void gol(int grid[NUM_ROWS][NUM_COLS]) {


    //for(int i = 0; i < 1000; ++i) {
    while(1) {
        print(grid);
        gol_step(grid);
        usleep(16000);
    }
}






void langdon_ant(int grid[NUM_ROWS][NUM_COLS])
{

    int x = NUM_ROWS/2;
    int y = NUM_COLS/2;
    int dir = 0;


    while(1) {
        print(grid);
        langdon_ant_step(grid,&x,&y,&dir);
        usleep(16000);
    }
}

void double_step(int grid[NUM_ROWS][NUM_COLS])
{
    int x = NUM_ROWS/2;
    int y = NUM_COLS/2;
    int dir = 0;


    while(1) {
        gol_step(grid);
        for(int i = 0; i < 20; ++i) {
            langdon_ant_step(grid,&x,&y,&dir);
            usleep(1600);
            print(grid);
        }
    }
}


int main() {
    int grid[NUM_ROWS][NUM_COLS];
    for(int i = 0; i < NUM_ROWS; ++i) {
        for(int j = 0; j < NUM_COLS; ++j) {
            if(grid[i][j] != 0) {
                grid[i][j] = 1;
            }
        }
    }
    //clear(grid);
    toad(grid,5,6);
    glider(grid,20,1);
    beacon(grid,2,30);



    double_step(grid);


    return 0;
}