# Use meshL to define an interval

**URL:** <https://community.freefem.org/t/use-meshl-to-define-an-interval/866>\
**Category:** General Discussion\
**Created:** [March 24, 2021, 10:19am UTC](https://community.freefem.org/t/use-meshl-to-define-an-interval/866 "2021-03-24T10:19:20Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Aicha](https://avatars.discourse-cdn.com/v4/letter/a/ec9cab/32.png) [@Aicha](https://community.freefem.org/u/Aicha)\
**Post date:** [March 24, 2021, 10:19am UTC](https://community.freefem.org/t/use-meshl-to-define-an-interval/866/1 "2021-03-24T10:19:20Z")

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Hi,  
please how we can youse meshL to define an interval [a,b]? Using segment.  
I don’t find examples.

Regards

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**Author:** ![gero](https://avatars.discourse-cdn.com/v4/letter/g/4491bb/32.png) [@gero](https://community.freefem.org/u/gero)\
**Post date:** [March 24, 2021, 1:18pm UTC](https://community.freefem.org/t/use-meshl-to-define-an-interval/866/2 "2021-03-24T13:18:00Z")

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> / using buildmeshL
> 
> real a = 2.0;  
> real b = 4.0;
> 
> int n=10;
> 
> border interval(t=a, b){x=t;y=0;z=0;};  
> meshL ThbuildmeshL = buildmeshL(interval(n));  
> fespace WhbuildmeshL(ThbuildmeshL,P1);  
> WhbuildmeshL B = x;
> 
> cout \<\< endl \<\< “buildmeshL” \<\< endl;  
> cout \<\< “x” \<\< endl \<\< B \<\< endl;

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<div class="post-metadata">

**Author:** ![Aicha](https://avatars.discourse-cdn.com/v4/letter/a/ec9cab/32.png) [@Aicha](https://community.freefem.org/u/Aicha)\
**Post date:** [March 24, 2021, 1:32pm UTC](https://community.freefem.org/t/use-meshl-to-define-an-interval/866/3 "2021-03-24T13:32:09Z")

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Hi gero,  
i’m lost with x. The interval is interval of time t.  
Then, can we change x by t? And in this case How we re-write  
border interval(t=a, b){x=t;y=0;z=0;};?

Othere question, can we use the expression “segment” to define meshL?

Regads

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**Author:** ![gero](https://avatars.discourse-cdn.com/v4/letter/g/4491bb/32.png) [@gero](https://community.freefem.org/u/gero)\
**Post date:** [March 24, 2021, 2:27pm UTC](https://community.freefem.org/t/use-meshl-to-define-an-interval/866/4 "2021-03-24T14:27:35Z")

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t is simply a parameter basically a variable.

I think [Parametric equation - Wikipedia](https://en.wikipedia.org/wiki/Parametric_equation) describes the mathematical concept behind it.

Kind regards  
gerald