Conversions to/from Symbolics?

[ChrisRackauckas]

This has been a piece that has been lacking a bit in Symbolics.jl right now. How specific is the IR here? How hard is it do convert to run the differentiation pass and convert back?

[asterycs]

This shouldn't be difficult. I actually wanted to implement this but I haven't managed yet. The variables are created here and for the conversion back to Symbolics one just needs to add something like this. The IR is already in standard form.

Some additional glue code would be needed for converting expressions created with Symbolics.

Not all features available in Symbolics are yet supported though, for example complex matrices and vectors.