| OK thanks for the answer. I totally agree with first class functions, and I probably agree with the Python-style ability to read outer variables (especially in the case that the inner call doesn't survive longer than the outer call). What I don't agree with is capturing locals to rebind them -- this is the explicit vs. implicit state argument. So for #1 map/filter, I don't really see this as a use case for closures. It's more about function literals and first-class functions. #2 I am on the fence about... I would be interested in examples. Like I said, with my somewhat limited JS experience, I understand why people like them, but I think you can do OK without mutating the surrounding scope. There's a distinction between calling a mutating method on an object in the surrounding scope, and actually rebinding something in the surrounding scope. #3 might be convincing although I would need examples. The Go-style defer is scope-based which seems more limited than general closures. Python's context managers are sort of a syntactic sugar/protocol around using certain kinds of classes -- much in the same way that iterators are. The other problem with closures it's not really one language feature -- they're different across languages. There is more than one issue with capture like the one with loops you mentioned in another comment. And, C++ now has closures, but there are a few different options with regard to LValues and RValues that I don't remember at the moment. It doesn't feel that solid to me, but I'll continue to play with it, and this chapter and some of the comments will certainly help. On the one hand, it seems like a ton of code has been written in C++, Java, and Python without closures. On the other hand, C++ and Java both added some closure-like features in the last decade, and Python added nonlocal, so that's probably a trend. (But like I said I've never actually seen anyone use nonlocal, it feels like something done "for completeness" rather than based on actual usage.) |