Consider switching to an expression structure like wolfram-expr

[jrmuizel]

Currently Woxi's enum Expr is a lot more complicated than the one in wofram-expr crate

My understanding is that wolfram-expr is a much closer match to Mathematica's internal representation. I think it would simplify things and reduce the likelihood of special casing to move to something more like wolfram-expr. It would help be stricter about what's evaluated when and should also avoid something like #83 by construction.

[jrmuizel]

Other Wolfram language implementations also use something more like wolfram-expr:
https://github.com/Mathics3/mathics-core/blob/eb3135b26fdd528d70f371ee66c55fd77bf2c369/mathics/core/expression.py#L251

https://github.com/poeschko/Mathador/blob/fefccc15f4933b66ac0210c63ddc8fb50cc64478/Expression.h#L65

[jrmuizel]

See also http://xahlee.info/M/WolframLang_principle.html

[jrmuizel]

I'm trying this out by first removing BinaryOp::Divide

[jrmuizel]

https://reference.wolfram.com/language/tutorial/SomeNotesOnInternalImplementation.html gives some more detail too.