Trouble with interacting components

Hi all! I'm trying to use Catalyst to model two interacting systems in `E. coli`: a nutrient sensor and a motor subsystem. The sensor measures nutrient concentrations `L` and outputs the target motor speed `λ`. The motor moves depending on `λ` and measures the nutrient concentration `L` based on the current position of the cell. In my case `λ` is best described as an observable, so I tried ```julia using Catalyst t = default_t() @variables L(t) λ(t) rec = @network_component rec begin @observables begin $λ ~ E / (E + Ep) end $(ParentScope(L)), E --> Ep 1., Ep --> 0 end mot = @network_component mot begin @equations begin D($(ParentScope(L))) ~ $(ParentScope(λ)) end end rn = complete(ReactionSystem(t; name=:rn, systems=[rec, mot])) u0 = [ rec.E => 0, rec.Ep => 10, L => 5 ] tmax = 100. prob = ODEProblem(rn, u0, (0, tmax); structural_simplify=true) ``` This yields ``` ERROR: ExtraVariablesSystemException: The system is unbalanced. There are 4 highest order derivative variables and 3 equations. More variables than equations, here are the potential extra variable(s): rec₊E(t) rec₊Ep(t) L(t) λ(t) Note that the process of determining extra variables is a best-effort heuristic. The true extra variables are dependent on the model and may not be in this list. ``` This is despite the system being well-defined (it can be written as an ODE in terms of E, Ep and L only. I am not sure how to eliminate λ. I'm not quite sure why `structural_simplify` is needed either, I guess this has to do with dependency resolution? Doing that manually (ouch) as follows: ```julia mot = @network_component mot begin @equations begin D($L) ~ $(rec.E) / ($(rec.E) + $(rec.Ep)) end end ``` yields ``` ERROR: LoadError: MethodError: no method matching recursive_escape_functions!(::QuoteNode, ::Vector{Union{Expr, Symbol}}) The function `recursive_escape_functions!` exists, but no method is defined for this combination of argument types. Closest candidates are: recursive_escape_functions!(!Matched::Union{Bool, Float64, Int64, Expr, Symbol}, ::Any) @ Catalyst ~/.julia/packages/Catalyst/8qDWw/src/dsl.jl:983 recursive_escape_functions!(!Matched::Union{Bool, Float64, Int64, Expr, Symbol}) @ Catalyst ~/.julia/packages/Catalyst/8qDWw/src/dsl.jl:983 in expression starting at /home/user/code/mcpop/models/chemotaxis/testall.jl:15 Stacktrace: (::Catalyst.var"#recursive_escape_functions!##0#recursive_escape_functions!##1"{Expr, Vector{Union{…}}})(i::Int64) at [dsl.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) foreach at [abstractarray.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) recursive_escape_functions!(expr::Expr, syms_skip::Vector{Union{Expr, Symbol}}) at [dsl.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) (::Catalyst.var"#recursive_escape_functions!##0#recursive_escape_functions!##1"{Expr, Vector{Union{…}}})(i::Int64) at [dsl.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) foreach at [abstractarray.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) recursive_escape_functions!(expr::Expr, syms_skip::Vector{Union{Expr, Symbol}}) at [dsl.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) (::Catalyst.var"#recursive_escape_functions!##0#recursive_escape_functions!##1"{Expr, Vector{Union{…}}})(i::Int64) at [dsl.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) foreach at [abstractarray.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) recursive_escape_functions!(expr::Expr, syms_skip::Vector{Union{Expr, Symbol}}) at [dsl.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) escape_equation!(eqexpr::Expr, all_syms::Vector{Union{Expr, Symbol}}) at [dsl.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) #get_rxexprs##2 at [dsl.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) foreach(f::Catalyst.var"#get_rxexprs##2#get_rxexprs##3"{Vector{Union{Expr, Symbol}}, Expr}, itr::Vector{Expr}) at [abstractarray.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) get_rxexprs(reactions::Vector{Catalyst.DSLReaction}, equations::Vector{Expr}, all_syms::Vector{Union{Expr, Symbol}}) at [dsl.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) make_reaction_system(ex::Expr, name::QuoteNode) at [dsl.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) make_rs_expr(name::QuoteNode, network_expr::Expr; complete::Bool) at [dsl.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) kwcall(::@NamedTuple{complete::Bool}, ::typeof(Catalyst.make_rs_expr), name::QuoteNode, network_expr::Expr) at [dsl.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) var"@network_component"(__source__::LineNumberNode, __module__::Module, name::Symbol, network_expr::Expr) at [dsl.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) eval(m::Module, e::Any) at [boot.jl](vscode-file://vscode-app/opt/vscodium-bin/resources/app/out/vs/code/electron-browser/workbench/workbench.html) ``` Adding `ParentScope` at random (I'm not sure how this works) doesn't fix anything. Any advice would be much appreciated!