# Checking for function notation f(7)

**URL:** <https://cl.desmos.com/t/checking-for-function-notation-f-7/4090>\
**Category:** Questions\
**Created:** [February 23, 2022, 4:07pm UTC](https://cl.desmos.com/t/checking-for-function-notation-f-7/4090 "2022-02-23T16:07:20Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Jeff\_Holcomb](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/jeff_holcomb/32/433_2.png) [@Jeff\_Holcomb](https://cl.desmos.com/u/Jeff_Holcomb)\
**Post date:** [February 23, 2022, 4:07pm UTC](https://cl.desmos.com/t/checking-for-function-notation-f-7/4090/1 "2022-02-23T16:07:20Z")

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I want to check that the S entered something like f(7). I can sort of get it to work by using the following.

fpattern = p.product(p.literal(`f`),p.number).strictOrder  
countNumberUsage(this.cellContent(4,1),7)=1

However, it will also validate with f\*7. I have tried using literal with parentheses:

fpattern = p.product(p.literal(`f`),p.lieral(`(`),p.number,p.literal(`)`).strictOrder

But no love. Ideas?

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**Author:** ![Jeff\_Holcomb](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/jeff_holcomb/32/433_2.png) [@Jeff\_Holcomb](https://cl.desmos.com/u/Jeff_Holcomb)\
**Post date:** [February 23, 2022, 4:51pm UTC](https://cl.desmos.com/t/checking-for-function-notation-f-7/4090/2 "2022-02-23T16:51:43Z")

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I can (duh) just do fpattern = p.literal(`f\left(7\right)`)

Maybe that’s the best approach??

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<div class="post-metadata">

**Author:** ![Daniel\_Grubbs](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/daniel_grubbs/32/719_2.png) [@Daniel\_Grubbs](https://cl.desmos.com/u/Daniel_Grubbs)\
**Post date:** [February 23, 2022, 6:21pm UTC](https://cl.desmos.com/t/checking-for-function-notation-f-7/4090/3 "2022-02-23T18:21:33Z")

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> [@Jeff\_Holcomb](#):
>
> Maybe that’s the best approach??

Seems that way to me. Once Desmos starts accepting function notation in the CL, then you’ll have an alternative.