void setup() {
    size(400,400);
    background(255);
}

void draw() {
    background(255);
    int[] pointA = {30,90};
    int[] pointB = {300, 240};
    cline(pointA,pointB);
};

void cline(int[] a, int[] b) {
    if (a[0] > b[0]) {
        int tmp = a[0];
        a[0] = b[0];
        b[0] = tmp;
    }
    if (a[1] > b[1]) {
        int tmp = a[1];
        a[1] = b[1];
        b[1] = tmp;
    };

    if (a == b) {
        point(a[0], a[1]);
    } else if (a[0] == b[0]) {
        for (int y = a[1]; y <= b[1]; y++) { point(a[0], y); }

    } else if (a[1] == b[1]) {
        for (int x = a[0]; x <= b[0]; x++) { point(x, a[1]); }

    } else {
        float vdif = (float) (b[1]-a[1])/(b[0]-a[0]);
        float y = a[0];
        println(vdif);
        for (int x = a[0]; x <= b[0]; x++) {
            point(x,y);
            y += vdif;
        }
    }
}