I’ve learned that nested functions are useful in Matlab to avoid passing tons of arguments to external functions when optimizing/fitting some data. Is this still true in Julia? Since lambda functions are very cheap, is there any point in nesting a function? What if I’m nesting 2 or 3 layers deep? T…

[image] rdeits: you do run the risk of running into performance of captured variables in closures · Issue #15276 · JuliaLang/julia · GitHub Wow, I did run into that. Thanks for the flag. OK, not nested it is.

Previously, I used a nested function definition also, but later I realized that I can get much better performance if I define the other function outside the main function, and use parametric typed to pass the extra information instead, so that lowered code is simplified for pre-compilation. This wou…

Don’t take this to mean “closures are slow” or that you shouldn’t use them if they suit your particular problem. It’s nearly always possible (if somewhat annoying) to avoid issue 15276 using a let block, as long as your closure (i.e. your nested function) doesn’t need to affect any bindings in the p…

If you need variables from the parent scope, the nested function is relatively short, and specific to where it’s used (can’t be reused elsewhere), I think nesting is a good idea. Disadvantages of nesting: If the nested function grows, readability of the parent function can be compromised (compare y…

[image] yakir12: I’ve been using it [try/catch] as a means to terminate a iteration that is fruitless. Since the mechanics of such an event is nested well down the code I can’t elicit a break or some such. But I can most certainly propagate some failure in another way. Hmm!!! @goto is your fr…

[image] foobar_lv2: In julia, @goto is not a necessarily a code smell, but instead is more fundamental than while and for (as evidenced by @code_lowered that rewrites control flow in terms of @goto ). This is not more or less true in any other languages that I’m aware of. Loops are also lower…

[image] kristoffer.carlsson: Using try catch for control flow is not great. This is generally true in other languages as well**. Pretty much all optimization specifically around exceptions are based on the assumption that they don’t happen often so they can be slow. (Of course on top of that …

[image] foobar_lv2: @goto is your friend Cool, I tried it now, but it seems that it won’t work across functions, right? I can’t @goto from one function to a @label in another function, right? If correct then this won’t work for me – breaking events occur inside functions other than the functi…

Even if you could (you cannot) – you would not want to do that. That is how “spaghetti code” is cooked.

Nested functions pros and cons

General Usage

kristoffer.carlsson January 9, 2019, 1:09pm 6

Using try catch for control flow is not great. It has performance implications and makes the code pretty confusing to read. Using a return value from raytrace! might work just as well here.

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Nested functions pros and cons

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