# A function question on CL

**URL:** <https://cl.desmos.com/t/a-function-question-on-cl/8050>\
**Category:** Questions\
**Tags:** simplefunction\
**Created:** [June 30, 2025, 1:27am UTC](https://cl.desmos.com/t/a-function-question-on-cl/8050 "2025-06-30T01:27:42Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![NTMDev](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/ntmdev/32/7141_2.png) [@NTMDev](https://cl.desmos.com/u/NTMDev)\
**Post date:** [June 30, 2025, 1:27am UTC](https://cl.desmos.com/t/a-function-question-on-cl/8050/1 "2025-06-30T01:27:42Z")

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I have used the `Action Button` a lot, but never used the `capture` sink. What does it do, and when would I use it?

Also, why use `parseEquation` when you can just use `simpleFunction`? From what I can see they look basically the same, but `parseEquation` is just harder to use.

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**Author:** ![Guzman\_Tierno](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/guzman_tierno/32/6149_2.png) [@Guzman\_Tierno](https://cl.desmos.com/u/Guzman_Tierno)\
**Post date:** [June 30, 2025, 8:41am UTC](https://cl.desmos.com/t/a-function-question-on-cl/8050/2 "2025-06-30T08:41:44Z")

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With capture you can create a list with the history of the values that a given variable took:

> **[Activity Builder by Desmos Classroom](https://classroom.amplify.com/activity/5eceb5abd1558c03b233131e/edit-readonly/published#step=395eb4c4-7b6a-4a2f-aa8b-b117728cb413&preview)**

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<div class="post-metadata">

**Author:** ![NTMDev](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/ntmdev/32/7141_2.png) [@NTMDev](https://cl.desmos.com/u/NTMDev)\
**Post date:** [June 30, 2025, 5:37pm UTC](https://cl.desmos.com/t/a-function-question-on-cl/8050/3 "2025-06-30T17:37:15Z")

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Thank you for answering my first question! But I can’t seem to find where the variables `a` and `b` are… also `history` seems pretty confusing.

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**Author:** ![Guzman\_Tierno](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/guzman_tierno/32/6149_2.png) [@Guzman\_Tierno](https://cl.desmos.com/u/Guzman_Tierno)\
**Post date:** [June 30, 2025, 6:30pm UTC](https://cl.desmos.com/t/a-function-question-on-cl/8050/4 "2025-06-30T18:30:37Z")

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the variables a and b in the example are inside the graph …  
history is a CL list containing all the captured values.

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<div class="post-metadata">

**Author:** ![NTMDev](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/ntmdev/32/7141_2.png) [@NTMDev](https://cl.desmos.com/u/NTMDev)\
**Post date:** [June 30, 2025, 10:44pm UTC](https://cl.desmos.com/t/a-function-question-on-cl/8050/5 "2025-06-30T22:44:10Z")

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Oh really? I think they are `number("a")` and `number("b")` correct?

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**Author:** ![system](https://canada1.discourse-cdn.com/flex031/uploads/desmos/original/2X/f/f5bd144684474e9a2f333002cde9840e52c5dbd3.png) [@system](https://cl.desmos.com/u/system)\
**Post date:** [July 2, 2025, 10:44pm UTC](https://cl.desmos.com/t/a-function-question-on-cl/8050/6 "2025-07-02T22:44:27Z")

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Closed on July 2, 2025, 10:44pm UTC

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