# JuMP model unregister action

**URL:** <https://discourse.julialang.org/t/jump-model-unregister-action/98784>\
**Category:** Optimization (Mathematical)\
**Tags:** question, jump\
**Created:** [May 13, 2023, 6:13am UTC](https://discourse.julialang.org/t/jump-model-unregister-action/98784 "2023-05-13T06:13:36Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Betristor](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/betristor/32/45264_2.png) [@Betristor](https://discourse.julialang.org/u/Betristor)\
**Post date:** [May 13, 2023, 6:13am UTC](https://discourse.julialang.org/t/jump-model-unregister-action/98784/1 "2023-05-13T06:13:36Z")

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I got a question about how JuMP expressions are constructed. Like I got an expression named `:a` defined on some variables `:x` and `:y` and some constants `:c` in the way like `a = x+y+c`. But later I want to do some modifications on `:c` to change it to a new `:c`. Firstly I unregister `:c` and then reinitialize it. If this time I constructed `:a` again using `a = x+y+c`, will `a` be `a = x+y+c` for the new `c` or `a = x+y+c+c'` where `c'` is the new one.

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**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [May 13, 2023, 10:50pm UTC](https://discourse.julialang.org/t/jump-model-unregister-action/98784/2 "2023-05-13T22:50:39Z")

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Can you provide a reproducible example of code with that you’re trying to achieve?

If you’re trying to modify the right-hand side of a constraint, you might want to look at `JuMP.set_normalized_rhs`.

See [Constraints · JuMP](https://jump.dev/JuMP.jl/stable/manual/constraints/#Modify-a-constant-term)