From 894f51ded83b3c21e44a80d7c0f3898778e84733 Mon Sep 17 00:00:00 2001
From: Dimitri Alston <123396563+DimitriAlston@users.noreply.github.com>
Date: Mon, 22 Jun 2026 14:19:46 -0400
Subject: [PATCH] Add function for `register_nlsystem` that doesn't require
 inequalities

---
 src/basefuncs.jl |  4 ++--
 src/userfuncs.jl | 22 ++++++++++++++++++----
 test/runtests.jl |  4 ++++
 3 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/src/basefuncs.jl b/src/basefuncs.jl
index 8865532..9ed86b2 100644
--- a/src/basefuncs.jl
+++ b/src/basefuncs.jl
@@ -11,7 +11,7 @@
 # systems.
 ################################################################################
 
-function mtk_generate_model_equations(sys::ModelingToolkit.System)
+function _generate_model_equations(sys::ModelingToolkit.System)
     param_dict = copy(ModelingToolkit.initial_conditions(sys))
     h = []
     for i in eachindex(ModelingToolkit.unknowns(sys))
@@ -30,7 +30,7 @@ function mtk_generate_model_equations(sys::ModelingToolkit.System)
     return h
 end
 
-function mtk_generate_reduced_expression(expr::Symbolics.Num, sys::ModelingToolkit.System)
+function _generate_reduced_expression(expr::Symbolics.Num, sys::ModelingToolkit.System)
     sub_dict = ModelingToolkit.initial_conditions(sys)
     for eqn in ModelingToolkit.observed(sys)
         sub_dict[eqn.lhs] = eqn.rhs
diff --git a/src/userfuncs.jl b/src/userfuncs.jl
index fa237f6..f53c37e 100644
--- a/src/userfuncs.jl
+++ b/src/userfuncs.jl
@@ -33,11 +33,11 @@ function and `Vector{Symbolics.Num}` constraints from a `ModelingToolkit.System`
 to a `JuMP.Model`.
 """
 function register_nlsystem(model::JuMP.Model, sys::ModelingToolkit.System, obj::Symbolics.Num, ineqs::Vector{Symbolics.Num})
-    h = EOptInterface.mtk_generate_model_equations(sys)
-    f = EOptInterface.mtk_generate_reduced_expression(obj, sys)
+    h = EOptInterface._generate_model_equations(sys)
+    f = EOptInterface._generate_reduced_expression(obj, sys)
     g = []
     for i in eachindex(ineqs)
-        gi = EOptInterface.mtk_generate_reduced_expression(ineqs[i], sys)
+        gi = EOptInterface._generate_reduced_expression(ineqs[i], sys)
         push!(g, gi)
     end
     JuMP.@constraint(model, [i in eachindex(h)], h[i](JuMP.all_variables(model)...) == 0)
@@ -46,12 +46,26 @@ function register_nlsystem(model::JuMP.Model, sys::ModelingToolkit.System, obj::
     return
 end
 
+"""
+    $(DocStringExtensions.TYPEDSIGNATURES)
+
+Automatically formulates and adds a user-provided `Symbolics.Num` objective 
+function from a `ModelingToolkit.System` to a `JuMP.Model`.
+"""
+function register_nlsystem(model::JuMP.Model, sys::ModelingToolkit.System, obj::Symbolics.Num)
+    h = EOptInterface._generate_model_equations(sys)
+    f = EOptInterface._generate_reduced_expression(obj, sys)
+    JuMP.@constraint(model, [i in eachindex(h)], h[i](JuMP.all_variables(model)...) == 0)
+    JuMP.@objective(model, Min, f(JuMP.all_variables(model)...))
+    return
+end
+
 """
     $(DocStringExtensions.TYPEDSIGNATURES)
 
 Automatically applies specified direct transcription method and registers the 
 discretized ODE `ModelingToolkit.System` as algebraic JuMP constraints.
-Current supports Explicit Euler "EE" and Implicit Euler "IE".
+Currently supports Explicit Euler "EE" and Implicit Euler "IE".
 """
 function register_odesystem(model::JuMP.Model, sys::ModelingToolkit.System, tspan::Tuple{Real,Real}, tstep::Real, integrator::String)
     if integrator != "EE" && integrator != "IE"
diff --git a/test/runtests.jl b/test/runtests.jl
index fef9a09..9c2b172 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -150,6 +150,10 @@ using Test
     @test JuMP.primal_status(model) == JuMP.FEASIBLE_POINT
     @test isapprox(JuMP.objective_value(model), 169869.99931631665, atol=1e-3)
 
+    model = JuMP.Model(Ipopt.Optimizer)
+    JuMP.@variable(model, xL[i] <= x[i=1:6] <= xU[i])
+    EOptInterface.register_nlsystem(model, system, obj)
+
 end
 
 @testset "ODE Model" begin