feat: build function with reactant

[avik-pal]

@ChrisRackauckas @AayushSabharwal can I get an initial review here? I will follow up with tests.

[ChrisRackauckas]

How does one compile those expressions?

[avik-pal]

How does one compile those expressions?

It is possible (though a bit annoying). My assumption was the expression == Val{true} case was more for diagnosis?

I can add a helper to compile MlirModule in reactant, which would mean you can do compile(returned_expr, args...)

[ChrisRackauckas]

Not really. It's more for caching so that the user can compile later, or use with precompilation.

[AayushSabharwal]

MTK only uses expression = Val{true} so it can control when and how things are compiled, along with being able to generate expressions that evaluate to the desired ODEProblem (as opposed to the ODEProblem itself). We can say that the latter is not supported with ReactantTarget but being able to control which module the code is compiled in is essential.

[avik-pal]

Can you point me to where this happens in MTK? We already have a serialization setup in Reactant which exports the expression into a standalone file.