Many languages have a notion of 'finalizers', but Racket has rather macabre 'will' functionality instead! https://docs.racket-lang.org/reference/willexecutor.html
Succinct and memorable, but 'will' is overloaded in English unfortunately.
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What are the most popular languages that have used an AST walker for their implementation?
I know Ruby used to do this, but there must be others.
(I'm interested in the lowest PL speed that users will tolerate if you have awesome features.)
Playing with optional type signatures in Python, I realise that the return type is the most important to me.
I'd much rather have a function with only a return type instead of a function with only parameter types. It's often quick to add too.
TIL Advent of Code and Project Euler will deliberately look for puzzles where the naive solution is worse than quadratic.
This ensures that people can solve them with any programming language. You don't want fast languages to be able to use the naive solution.