# Using anonymous and or symbols to create dynamic variable names?

**URL:** https://discourse.julialang.org/t/using-anonymous-and-or-symbols-to-create-dynamic-variable-names/83095
**Category:** Optimization (Mathematical)
**Tags:** jump
**Created:** [June 20, 2022, 10:13pm UTC](https://discourse.julialang.org/t/using-anonymous-and-or-symbols-to-create-dynamic-variable-names/83095 "2022-06-20T22:13:59Z")
**Posts on this page:** 1
**Showing post:** 3

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### Author: ![pierre-haessig](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pierre-haessig/32/217129_2.png) [@pierre-haessig](https://discourse.julialang.org/u/pierre-haessig)
#### Post date: [June 14, 2024, 2:40pm UTC](https://discourse.julialang.org/t/using-anonymous-and-or-symbols-to-create-dynamic-variable-names/83095/3 "2024-06-14T14:40:32Z")

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> [@odow](#):
>
> > in no case can you dynamically create a binding like `x_i`
> 
> By this this I _really_ mean it.

Hello,  
I’m resurrecting this 2022 thread because I’d like to be sure what you mean by _“I really mean it”_ 😉 …

Indeed, I read the JuMP doc section [Design patterns for larger models](https://jump.dev/JuMP.jl/stable/tutorials/getting_started/design_patterns_for_larger_models/) (that you mentioned in another question related to variable name collision [How to merge two `JuMP` models?](https://discourse.julialang.org/t/how-to-merge-two-jump-models/113646)) but also the very useful [String names, symbolic names, and bindings](https://jump.dev/JuMP.jl/stable/manual/variables/#variable_names_and_bindings) section and at the end it says:

> - You can manually register names in the model via `model[:key] = value`

So my question is the following: in the context of a multi-stage optimization problem where each stage contains about the same variables and contraints, I’d be tempted to dynamically forge variable names like: variable `x` for stage 1 should be `x1`…

Using anonymous variables + `Dict` containers (with names as keys), I can get such variables defined (and the String name attribute can be freely set as a bonus).

However, I’ve also tested the idea of manual registration using a dynamically created `Symbol(variable_name)`. I understand that it’s not needed since I can already access variables in my Dicts, but this dynamic registration _does work_, so that’s why I’m asking your advice: is the manual registration of dynamically created `Symbol`s:

- a bad practice (due to potential name clashes)?
- or it can seriously break some lower level JuMP layers?

* * *

Here is a code example to illustrate: I want to have variable `x1` and `x2` created dynamically:

```julia
using JuMP
using HiGHS

"add variable `name` to model `m` and to Dict `dat`, for optional `stage`"
function add_stage_variable!(m::Model, dat::Dict{String,Any}, name::String; stage="")
    name_suffix = "$name$stage"
    dat[name] = @variable(m, base_name=name_suffix) # here I can use name or name_suffix
    # Optional last line: finish the job by registering variable as name_suffix????
    m[Symbol(name_suffix)] = dat[name]
end

m = Model(HiGHS.Optimizer)
set_silent(m)
data1 = Dict{String,Any}() # container for 1st stage variables
data2 = Dict{String,Any}() # container for 2nd stage variables
add_stage_variable!(m, data1, "x"; stage=1)
add_stage_variable!(m, data2, "x"; stage=2)

```

and the end of this code, `data1` gets printed as `Dict{String, Any}("x" => x1)`. In fact, by modifying `add_stage_variable!`, it could have been `"x" => x1`, `"x1" => x1`, `"x1" => x` or `"x" => x` depending on taste, since there is no risk of clash with the content of `data2`.

And the model `m` prints as:

```julia
A JuMP Model
Feasibility problem with:
Variables: 2
Model mode: AUTOMATIC
CachingOptimizer state: EMPTY_OPTIMIZER
Solver name: HiGHS
Names registered in the model: x1, x2

```

and that last line disappears if I comment out the last line of `add_stage_variable!` function.

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