# Expression Component syntax

**URL:** <https://discourse.mcneel.com/t/expression-component-syntax/77851>\
**Category:** Grasshopper\
**Tags:** grid, surface, loft, points\
**Created:** [January 25, 2019, 4:32am UTC](https://discourse.mcneel.com/t/expression-component-syntax/77851 "2019-01-25T04:32:53Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![ann.staniford](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/ann.staniford/32/153686_2.png) [@ann.staniford](https://discourse.mcneel.com/u/ann.staniford)\
**Post date:** [January 25, 2019, 4:32am UTC](https://discourse.mcneel.com/t/expression-component-syntax/77851/1 "2019-01-25T04:32:53Z")

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Im not sure what to type into the expression next to the U on SrfGrid im trying to make a surface over a grid of points and i copied the definition from someone and they didnt put what to enter into the expression  
HELPPPP!!

 ![Canvas%20at%2022%3B27%3B29](https://global.discourse-cdn.com/mcneel/original/3X/4/4/44109178890fc4440fb76c68e78dab432d9a41fc.png)

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**Author:** ![Baris](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/baris/32/759711_2.png) [@Baris](https://discourse.mcneel.com/u/Baris)\
**Post date:** [January 25, 2019, 4:50am UTC](https://discourse.mcneel.com/t/expression-component-syntax/77851/2 "2019-01-25T04:50:16Z")

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It’s X+1

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**Author:** ![ann.staniford](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/ann.staniford/32/153686_2.png) [@ann.staniford](https://discourse.mcneel.com/u/ann.staniford)\
**Post date:** [January 25, 2019, 5:00am UTC](https://discourse.mcneel.com/t/expression-component-syntax/77851/3 "2019-01-25T05:00:32Z")

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Thank you that helped, but it only made it orange and the alter is that the expression did not return a valid value for 40. Do you know what that means? It wont let me bake it.

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**Author:** ![HS\_Kim](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/hs_kim/32/473975_2.png) [@HS\_Kim](https://discourse.mcneel.com/u/HS_Kim)\
**Post date:** [January 25, 2019, 5:50am UTC](https://discourse.mcneel.com/t/expression-component-syntax/77851/4 "2019-01-25T05:50:24Z")

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Check attachment.

 ![Canvas%20at%2014%3B48%3B07](https://global.discourse-cdn.com/mcneel/original/3X/6/c/6cbf6f8877ecd0f0c0a70a362204db05cd7ab97f.png)  
[MathSurface\_re.gh](https://global.discourse-cdn.com/mcneel/uploads/default/original/3X/d/4/d4244bec76069bf620a5c97e71ea990c15f974ff.gh) (6.2 KB)

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**Author:** ![Modeler3D](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/modeler3d/32/486828_2.png) [@Modeler3D](https://discourse.mcneel.com/u/Modeler3D)\
**Post date:** [January 26, 2019, 2:55am UTC](https://discourse.mcneel.com/t/expression-component-syntax/77851/5 "2019-01-26T02:55:57Z")

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And how can I learn to write similar mathematical expressions?