Adding optional symbolic package to svFSIplus

[zasexton]

Use Case

There is a need to include symbolic manipulation into svFSIplus for custom implementations of the advection-reaction-diffusion equation (and potentially future constitutive models). See #218 (comment)

Problem

Figuring out how to include a symbolic library in a way that is efficient and not cumbersome to the rest of the svFSIplus project will be important. Many such packages can be large, involving many other dependencies -- we do not want this.

Solution

We plan to optionally adopt SymEngine, which is a standalone fast C++ symbolic manipulation library, for the symbolic manipulation of custom reactive terms that may be explored in custom implementations of the advection-diffusion-reaction equation. We plan to include this library as an optional Fetch dependency during configuration using cmake's FetchContent functionality. This might also outline a good template for interfacing other packages with svFSIplus without having to explicitly include them in the code base.

Alternatives considered

None so far....other symbolic libraries are typically larger and more difficult to integrate.

Additional context

No response

Code of Conduct

• I agree to follow this project's Code of Conduct and Contributing Guidelines

[zasexton]

an initial implementation has been built that correctly compiles svFSIplus with symengine here: https://github.com/zasexton/svFSIplus_public/tree/add-symengine-%23238