Langton's Ant

ant.c

#include <assert.h>
#include <stdio.h>
#include <time.h>

#define LONG_SPACED_STRING                                                     \
  "          "                                                                 \
  "          "                                                                 \
  "          "                                                                 \
  "          "                                                                 \
  "          "                                                                 \
  "          "                                                                 \
  "          "                                                                 \
  "          "

#define CLRSCR() printf("\033[1;1H\033[2J")

static char map[80][81] = {
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING, LONG_SPACED_STRING,
    LONG_SPACED_STRING, LONG_SPACED_STRING,

};

typedef enum
{
    RIGHT = 0,
    DOWN  = 1,
    LEFT  = 2,
    UP    = 3
} AntDirection;

static void
PrintMap(void)
{
    int i;
    for (i = 0; i < 80; i++)
        printf("%s\n", map[i]);
}

int
main(void)
{
    unsigned int antX = 40;
    unsigned int antY = 40;
    int          i;
    char         mapPos;
    AntDirection direction = RIGHT;

    struct timespec req;
    req.tv_sec  = 0;
    req.tv_nsec = 62500000L / 4;

    for (i = 0; i < 11000; i++)
    {
        assert(antX < 80 && antY < 80);
        CLRSCR();

        mapPos = map[antY][antX];
        if (mapPos == '#')
        {
            mapPos    = ' ';
            direction = (direction + 1) % 4;
        }
        else
        {
            mapPos    = '#';
            direction = (direction - 1) % 4;
        }

        map[antY][antX] = '@';
        PrintMap();
        map[antY][antX] = mapPos;

        switch (direction)
        {
        case UP:
            antY--;
            break;
        case DOWN:
            antY++;
            break;
        case LEFT:
            antX--;
            break;
        case RIGHT:
            antX++;
            break;
        }

        nanosleep(&req, NULL);
    }

    return 0;
}