Syntax for mathematical expressions in model definitions

[sbenthall]

A desideratum for future versions of HARK is a syntax for mathematical expressions in model definitions.

This syntax need not be the native Python syntax, though this is what is done in @llorracc 's "pre-alpha 2.0" code, which uses strings of Python and the very controversial eval function to parse them.

https://github.com/econ-ark/HARK/pull/1055

Dolo has its own Dolang syntax and interpreter, which is an attractive choice. I wonder if it can be extracted from the YAML context in which it is used.

In conversation with @alanlujan91 and @nicksawhney , Disciplined Convex Programming (DCP) has come up. This is a DSL for convex optimization problems developed by researchers at Stanford. It is implemented in several convex optimization packages, in different languages.

https://www.cvxpy.org/tutorial/dcp/index.html

DCP has the advantage of being featureful with respect to convex optimization -- if it can be expressed in the language, then it guarantees that it can be solved by their optimization engine (in this case CVXPY).