# How to make a variable decrease then increase when it reaches a point

**URL:** <https://discourse.processing.org/t/how-to-make-a-variable-decrease-then-increase-when-it-reaches-a-point/35442>\
**Category:** Processing.py\
**Created:** [February 25, 2022, 11:28am UTC](https://discourse.processing.org/t/how-to-make-a-variable-decrease-then-increase-when-it-reaches-a-point/35442 "2022-02-25T11:28:35Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![adora](https://avatars.discourse-cdn.com/v4/letter/a/a8b319/32.png) [@adora](https://discourse.processing.org/u/adora)\
**Post date:** [February 25, 2022, 11:28am UTC](https://discourse.processing.org/t/how-to-make-a-variable-decrease-then-increase-when-it-reaches-a-point/35442/1 "2022-02-25T11:28:35Z")

</div>

So I have my variable x and I want it to keep on decreasing until it reaches 10 and then start increasing to 50 then go back to 10 and keep on repeating (e.g. 12, 11, 10, 11, 12, 13, …, 49, 50, 49, 48, …, 11, 10).

This was my code:

```auto
    if x = 10:
        x = x + 1
    else:
        x = x - 1

```

But then I realised this wouldn’t work since x would just end up being 10, 11, 10, 11…, so now I’m not so sure what to do. Does anyone know what the easiest way I can do this is? Thank you very much 🙂

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<div class="post-metadata">

**Author:** ![GoToLoop](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/gotoloop/32/86_2.png) [@GoToLoop](https://discourse.processing.org/u/GoToLoop)\
**Post date:** [February 25, 2022, 11:41am UTC](https://discourse.processing.org/t/how-to-make-a-variable-decrease-then-increase-when-it-reaches-a-point/35442/2 "2022-02-25T11:41:12Z")

</div>

> [@adora](#):
>
> Does anyone know what the easiest way I can do this is?

You could have a 2nd variable which would store the value that _x_ would use to increase or decrease.

And then invert its signal value when _x_ reaches any of the minimum & maximum limits:

## Python Mode:

```auto
MIN_X, MAX_X = 10, 50
x, incX = MIN_X, 1

def setup():
    frameRate(5)

def draw():
    global x, incX
    this.print(x, incX, TAB)
    x += incX
    if x == MIN_X or x == MAX_X: incX *= -1

```

## Java Mode:

```auto
static final int MIN_X = 10, MAX_X = 50;
int x = MIN_X, incX = 1;

void setup() {
  frameRate(5);
}

void draw() {
  print(x, incX, TAB);
  x += incX;
  if (x == MIN_X || x == MAX_X) incX *= -1;
}

```

p5.js Mode:

```auto
const MIN_X = 10, MAX_X = 50;
var x = MIN_X, incX = 1;

function setup() {
  frameRate(5);
}

function draw() {
  print(x, incX);
  x += incX;
  if (x == MIN_X || x == MAX_X) incX *= -1;
}

```

---

<div class="post-metadata">

**Author:** ![villares](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/villares/32/3166_2.png) [@villares](https://discourse.processing.org/u/villares)\
**Post date:** [February 25, 2022, 12:53pm UTC](https://discourse.processing.org/t/how-to-make-a-variable-decrease-then-increase-when-it-reaches-a-point/35442/3 "2022-02-25T12:53:22Z")

</div>

I think the solution from @GoToLoop is brilliant, as usual, and even compares to Java mode and JavaScript (p5js) which can be very helpful for people using the other modes.

I’ve used his code but changed the variable names to something I would use myself in class, and tried some variations on the syntax, nothing essential changed, see if this helps:

```python
MIN_X, MAX_X = 10, 50
x = MIN_X
direction = 1

def setup():
    frameRate(5)

def draw():
    global x, direction
    println("x:{} direction:{}".format(x, direction))
    x = x + direction # same as x += direction
    if x == MIN_X or x == MAX_X:
        direction = -direction # same as direction *= -1

```