notes

Prewalk and PostWalk.
Does a walk.x

# TODO (in no particular order)
0. Resolve serious disagreements on the nature of validation beyond types. The possibility of internal type conversion, types of types and their handling, shittyness of python typing module.
1. Different types of iteration methods: depth vs. breadth, external or internal, dup vs no dup, dup notion, ocality, local ordering, Nones, Names, Flattening. General Collections.abc interfance questions (sets, functions, etc...)
2. The problem of matching over an IR that does not yet exist.
3. Extension of existing ADTs or merging of ADTS
4. Basic documentation.
5. Vistior patterns
6. Custom show or at least better show. 
7. Python front end instead of text. See (2).
8. Functorial IRs
9. Logging intergration
10. Github integrations
11. Variations on the lambda calc implementation for examples. Add these to tests.
12. Attrs vs. Dataclasses. Attrs might save some boiler plate, but it outside standard python.
13. Greater variation on internal errors and consistenty with python.
14. psf black
15. Ref Mutability and selective mutalability/frozeness - ability to express cfg
16. Integration with mypy/pyright/whwatever
17. Function recursion helpers
18. Folding/tree systems


Pretty printing:
Expr, stmt, graph

Preable (subst)