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When everything is scoped dynamically, it is indeed a problem. If you only have a handful of things with a clear syntactic mechanism to indicate when they are b
by jdougan 3y ago
When everything is scoped dynamically, it is indeed a problem. If you only have a handful of things with a clear syntactic mechanism to indicate when they are being used? Much clearer.
I impkemented a slow version of contexts in Smalltalk, just to see how bad it was. Where it shone was in places where you can't pass a context as an arg (eg. binary math operators) either for compatibility reasons or because passing the context would be too noisy.
- duped 3y agoI disagree it's clearer, because it's a spooky action at a distance. An analog are thread locals, which have the same characteristics of a dynamically scoped variable. I've found dynamic scoping useful so few times I can count them on one hand, and while it's an intriguing feature, I think it makes a lot of sense to use a more explicit abstraction. For example, you shouldn't need dynamic scoping for overloading binary operators - you should have a more clear method that takes a context as an argument instead. Context is external state, and it's extremely surprising when a fundamental operator like "+" modifies it.