Determine how to make bound-style alpha substitution work with hash consing

[kozross]

bound provides a really good method to simplify alpha substitution and perform it efficiently. While we may not use bound itself, its approach should 100% be part of how Covenant is represented in Haskell. However, a disadvantage of bound is that it forces a tree-like structure on anything it's used with.

This can be quite inefficient for sharing, which bloats representation size and potentially makes it more difficult for tooling to work. In particular, it inhibits hash consing, which we ideally would like to be possible.

We need to investigate how the bound approach (even in a simplified form) could be combined with hash consing, or if it's not possible, what exactly blocks it.

[itsfarseen]

@kozross My plan is to:

• Define a simple lambda calculus interpreter
• Implement hash consing.
• Investigate how to implement alpha substitution by referring to bound and other general ways to do it.

Does this sound good?

[kozross]

@itsfarseen - seems good to me. Let us know what you find.