# What does this error message mean?

**URL:** <https://discourse.processing.org/t/what-does-this-error-message-mean/47370>\
**Category:** Beginners\
**Created:** [October 15, 2025, 6:01pm UTC](https://discourse.processing.org/t/what-does-this-error-message-mean/47370 "2025-10-15T18:01:17Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![WillyGrz](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WillyGrz](https://discourse.processing.org/u/WillyGrz)\
**Post date:** [October 15, 2025, 6:01pm UTC](https://discourse.processing.org/t/what-does-this-error-message-mean/47370/1 "2025-10-15T18:01:17Z")

</div>

\<  
if (projXmove \>= (displayWidth/75)/sqrt(1+(projSlope)(projSlope))) {  
projXmove = (displayWidth/75)/sqrt(1+(projSlope)(projSlope));  
}

> 

When I try to run this within my program I get the error message “The operator + is undefined for the argument type(s) int, projSlope”

I’m not sure what that means. I feel it may be related to trying to use 1 as an integer value with float type variables, but i’m not otherwise sure how I would fix this.

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<div class="post-metadata">

**Author:** ![quark](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/quark/32/26_2.png) [@quark](https://discourse.processing.org/u/quark)\
**Post date:** [October 15, 2025, 6:15pm UTC](https://discourse.processing.org/t/what-does-this-error-message-mean/47370/2 "2025-10-15T18:15:58Z")

</div>

I suspect you are using JAVA mode so your code should probably be like this

```auto
if (projXmove >= (displayWidth / 75) / sqrt(1 + projSlope * projSlope)) {
  projXmove = (displayWidth / 75) / sqrt(1 + projSlope * projSlope);
}

```

Notice the mutiplication sign (`*`), you seem to have missed these.

Also in this instance the brackets surrounding `projSlope` are superfluous and I have added white-space round the math operators for clarity.

This assumes that `projXmove` and `projSlope` are both of type `float`.

In terms of programming logic I believe you can replace the code with the following.

```auto
projXmove = max(projXmove, (displayWidth / 75) / sqrt(1 + projSlope * projSlope));

```

I leave you to work out why 😁

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<div class="post-metadata">

**Author:** ![glv](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/glv/32/18785_2.png) [@glv](https://discourse.processing.org/u/glv)\
**Post date:** [October 15, 2025, 6:19pm UTC](https://discourse.processing.org/t/what-does-this-error-message-mean/47370/3 "2025-10-15T18:19:57Z")

</div>

> [@quark](#):
>
> Notice the mutiplication sign (`*`), you seem to have missed these.

This is sometimes from incorrect formatting of code.  
Or just an error.

@WillyGrz ,

Please read:

- _[Welcome to the Processing Foundation Discourse](https://discourse.processing.org/t/welcome-to-the-processing-foundation-discourse/8)_
- _[Guidelines—Asking Questions](https://discourse.processing.org/t/guidelines-asking-questions/2147)_ \< Discusses formatting

Your code is not formatted correctly.

`:)`

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<div class="post-metadata">

**Author:** ![quark](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/quark/32/26_2.png) [@quark](https://discourse.processing.org/u/quark)\
**Post date:** [October 15, 2025, 6:25pm UTC](https://discourse.processing.org/t/what-does-this-error-message-mean/47370/4 "2025-10-15T18:25:17Z")

</div>

@glv thanks for the comment about formatting, forgot about that 😉

> [@WillyGrz](#):
>
> When I try to run this within my program I get the error message “The operator + is undefined for the argument type(s) int, projSlope”

Sorry my answer was incomplete. Since you are performing maths the `+` sign expects a numeric literal or numeric variable for both arguments so I suspect that the variable `projSlope` is not a numeric variable.