# Assertion fail (iseuil) when trunc

**URL:** <https://community.freefem.org/t/assertion-fail-iseuil-when-trunc/1565>\
**Category:** General Discussion\
**Created:** [March 1, 2022, 11:57am UTC](https://community.freefem.org/t/assertion-fail-iseuil-when-trunc/1565 "2022-03-01T11:57:35Z")\
**Posts on this page:** 1\
**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:** [March 1, 2022, 11:57am UTC](https://community.freefem.org/t/assertion-fail-iseuil-when-trunc/1565/1 "2022-03-01T11:57:35Z")

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Dear developper,

I encounter an assertion fails with some 2D meshes that I didn’t have before. Again these problems with the trunc function (which should be combinatorial, not ?)!  
[Th.o.mesh](https://community.freefem.org/uploads/short-url/wT6OUYrF9qDJwPTVm2OoF0B1KDk.mesh) (197.0 KB)

The following code fails:

```nohighlight
mesh Th=readmesh("Th.o.mesh");
mesh Thf=trunc(Th,region==3);

```

Many thanks in advance for your help.

Regards