# Procedural Nonlinear Constaint Generation - String to NLconstraint

**URL:** https://discourse.julialang.org/t/procedural-nonlinear-constaint-generation-string-to-nlconstraint/34799
**Category:** Optimization (Mathematical)
**Tags:** jump, optim, optimization
**Created:** [February 18, 2020, 9:08am UTC](https://discourse.julialang.org/t/procedural-nonlinear-constaint-generation-string-to-nlconstraint/34799 "2020-02-18T09:08:43Z")
**Posts on this page:** 1
**Showing post:** 4

<div class="post-metadata">

### 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: [February 20, 2020, 4:01pm UTC](https://discourse.julialang.org/t/procedural-nonlinear-constaint-generation-string-to-nlconstraint/34799/4 "2020-02-20T16:01:29Z")

</div>

```nohighlight
using JuMP

substitute_args(ex, vars) = ex
substitute_args(ex::Symbol, vars) = get(vars, ex, ex)
function substitute_args(ex::Expr, vars)
    for (i, arg) in enumerate(ex.args)
        ex.args[i] = substitute_args(arg, vars)
    end
    return ex
end

model = Model()
@variable(model, x[1:2])
str = "x1^3 + 5 * x1 * x2"
ex = Meta.parse(str)
vars = Dict(:x1 => x[1], :x2 => x[2])

set_NL_objective(
    model, 
    MOI.MIN_SENSE,
    substitute_args(ex, vars)
)

```

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