# Hyphens/Dashes in variable name

**URL:** <https://community.freefem.org/t/hyphens-dashes-in-variable-name/2388>\
**Category:** Feature Request\
**Created:** [April 11, 2023, 11:07am UTC](https://community.freefem.org/t/hyphens-dashes-in-variable-name/2388 "2023-04-11T11:07:01Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![ffeppon](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/ffeppon/32/1011_2.png) [@ffeppon](https://community.freefem.org/u/ffeppon)\
**Post date:** [April 11, 2023, 11:07am UTC](https://community.freefem.org/t/hyphens-dashes-in-variable-name/2388/1 "2023-04-11T11:07:01Z")

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Dear developers,

So far, it seems that FreeFEM does not allow variable names with hyphens or dashes, for instance:

```c++
real a_variable_with_hyphens = 3;

```

Is there a good reason for this ? Sometimes, using hyphens improves readability over the use of capital letters. Although this is certainly not an urgent feature to add, this would be nice to do, unless there is a very good reason for this.

Regards  
Florian

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**Author:** ![zhugp123](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@zhugp123](https://community.freefem.org/u/zhugp123)\
**Post date:** [April 11, 2023, 3:45pm UTC](https://community.freefem.org/t/hyphens-dashes-in-variable-name/2388/2 "2023-04-11T15:45:15Z")

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The FF document explains this point and you may check it.

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**Author:** ![cmd](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/cmd/32/67_2.png) [@cmd](https://community.freefem.org/u/cmd)\
**Post date:** [April 11, 2023, 8:06pm UTC](https://community.freefem.org/t/hyphens-dashes-in-variable-name/2388/3 "2023-04-11T20:06:28Z")

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See [here](https://doc.freefem.org/references/index.html#language-references): "

> The variable name is just an alphanumeric string, the underscore character `_` is not allowed, because it will be used as an operator in the future.

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<div class="post-metadata">

**Author:** ![ffeppon](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/ffeppon/32/1011_2.png) [@ffeppon](https://community.freefem.org/u/ffeppon)\
**Post date:** [April 12, 2023, 7:04am UTC](https://community.freefem.org/t/hyphens-dashes-in-variable-name/2388/4 "2023-04-12T07:04:56Z")

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Thanks !  
And does anyone happen to know to what kind of operator the underscore will implement ?

Best

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**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\
**Post date:** [April 12, 2023, 7:19am UTC](https://community.freefem.org/t/hyphens-dashes-in-variable-name/2388/5 "2023-04-12T07:19:41Z")

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It is supposed to be for automatic differentiation.

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<div class="post-metadata">

**Author:** ![ffeppon](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/ffeppon/32/1011_2.png) [@ffeppon](https://community.freefem.org/u/ffeppon)\
**Post date:** [April 17, 2023, 8:54am UTC](https://community.freefem.org/t/hyphens-dashes-in-variable-name/2388/6 "2023-04-17T08:54:11Z")

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Thanks, this is clear. Looking forward to see this in a coming future then.