// PROGRAM ca1
// one-dimensional Boolean cellular automata

int main();
void setrule(int update[]);
void initial(int site[], int *L, int *tmax);
void iterate(int site[], int L, int update[], int tmax);

#define MAXWIDTH 1600

int main()
{
    int L, site[MAXWIDTH], tmax, update[8], Itmp1_;

    for(Itmp1_ = 0; Itmp1_ < MAXWIDTH; ++Itmp1_)
        site[Itmp1_] = 0;

    setrule(update);
    initial(site, &L, &tmax);
    iterate(site, L, update, tmax);

    return 0;
}

void setrule(int update[])
{
    int bit0, bit1, bit2, i, rule;

    rule=90;
    printf("rule number = %d\n", rule);
    for(i = 7; i >= 0; --i)
    {
        update[i] = (rule >> i);            // find binary representation
        rule = rule - (update[i] << i);
        bit2 = i/4;
        bit1 = (i - 4*bit2)/2;
        bit0 = i - 4*bit2 - 2*bit1;
        // show possible neighborhoods
        printf("%1d %1d %1d ", bit2, bit1, bit0);
        printf("   ");
    }
    printf("\n");
    for(i = 7; i >= 0; --i)
    {
        printf(" %2d ", update[i]);          // print rules
        printf("     ");
    }
    printf("\n");
}

void initial(int site[], int *L, int *tmax)
{

    (*L) = 60;
    (*tmax) = 100;
    site[(*L)/2] = 1;                       // center site

}

void iterate(int site[], int L, int update[], int tmax)
{
    int i, index, sitenew[MAXWIDTH], t, Itmp1_;

    // update lattice
    // need to introduce additional array, sitenew, to temporarily
    // store values of newly updated sites
    for(t = 1; t <= tmax; ++t)
    {
        for(i = 1; i <= L; ++i)
        {
            index = 4*site[i - 1] + 2*site[i] + site[i + 1];
            sitenew[i] = update[index];
            if(sitenew[i] == 1) printf("X");
	    else printf(".");
        }
	printf("\n");
        for(Itmp1_ = 0; Itmp1_ < MAXWIDTH; ++Itmp1_)
            site[Itmp1_] = sitenew[Itmp1_];
        site[0] = site[L];                  // periodic boundary conditions
        site[L + 1] = site[1];
    }
}