Processing `constrain()` tests.

constrain.pde

float x = 0;
float y = 0;
float speed = 0.9;


void setup(){
}


void draw(){
    x = x + speed;
    y = y + speed;
    float prevx = x;
    float prevy = y;
    x = constrain(x, 0, width);
    y = constrain(y, 0, height);

    if (x != prevx || y != prevy){
        speed = speed * -1;
    } else {
        println("x: " + x, "prevx: " + prevx);
        println("y: " + y, "prevy: " + prevy);
    }
    ellipse(x, y, 15, 15);
}

constrain.pyde

x = 0.0
y = 0.0
speed = 0.9


def setup():
    pass


def draw():
    x += speed
    y += speed
    prevx = x
    prevy = y
    x = constrain(x, 0, width)
    y = constrain(y, 0, height)
    if x != prevx or y != prevy:
        print('x: {0}, prevx: {1}'.format(x, prevx))
        print('y: {0}, prevy: {1}'.format(y, prevy))
        speed *= -1
    ellipse(x, y, 15, 15)