The C++ Lambdas

[@HomeofLawboy]

This is pretty high quality, hope this channel grows a lot

[@bsdooby]

Awesome 🎉 as always; and yes to Concepts 👍

[@zamf]

Lambdas are my favourite feature of C++. They enable so much expressiveness and because of them some consider C++ to be a functional programming language (or at least a programming language that can be written in a functional style).
You should also do a video on std::function, which combined with lambdas makes for some really powerful coding patterns.
Also, in C++23 they introduced std::move_only_function, which is a more optimized version of std::function for captured objects that are not copyable.
And in C++26 they're introducing std::function_ref, which is a light-weight version of std::function.
As for lambdas, it should be noted that they can be templated as well.
And one more important thing about lambdas is that they return their result by value by default, meaning that if you want a lambda that returns a reference you need to specify its return type as "auto&" or "decltype(auto)" or something similar to this.

[@CodeForYourself]

@@zamf thanks! All good points! I’m still mostly targeting C++17 here just to make sure I have something finished before moving on to new standards. So no goodies that you described.
Also, I’m not trying to completely copy cppreference here. The aim is to give people enough knowledge to be able to dig further. Hope this explains a bit better some choices I make in these videos.

[@zamf]

​@@CodeForYourself I agree. I just think that std::function is a good candidate for a future video as a follow up to this one.

[@CodeForYourself]

@@zamf definitely. That video I really want to record at some point but a proper deep dive into how it works requires type erasure and I’m not sure how long it will take me to distill it into a manageable explanation 😅

[@Maximus98245]

The biggest issue with std::function is that it doesn't respect the const-ness (other than a smaller issue of it might need to allocate and takes up 32 bytes as opposed to 8 for function pointer)
struct Functor { int x = 0; void operator()() { ++x; } };
const Functor func;
//func(); // good, this will not compile
const std::function stdfunc = Functor{};
stdfunc(); // compiles, I can mutate const
std::println("stdfunc.target()->x == {}", stdfunc.target()->x);

[@zamf]

@@Maximus98245 That is weird, I agree. But it's a similar behaviour to const pointers and even to const std::reference_wrapper. So not that unexpected.
At least it modifies a local copy of the data, so nothing else in the program is modified.

I'd appreciate a lecture on concepts! Bare templates are a bit confusing and their error messages are confusing. I guess concepts help with understanding what the types are for in the template.

[@CodeForYourself]

Yes, exactly. Let’s see if I get to record a video about this.

[@Maximus98245]

Great content! Yes to Concepts!! and multi-threading..and coroutines too..ok, I am pushing it I know...

[@CodeForYourself]

@@Maximus98245 coroutines probably won’t happen. Everything else might 😉

[@zamf]

@@CodeForYourself Yeah, coroutines are for library developers. Not something that can be explained in a 10-20 minute youtube video.

[@viktordiadkov8768]

Amazing! comment to promote

[@CodeForYourself]

@@viktordiadkov8768 thanks! Highly appreciate it! 🙌

[@segfault4568]

Great video, would be nice to cover function pointers and std::functions also the differences and use cases.

[@CodeForYourself]

@@segfault4568 yes, absolutely! I hope to be able to get to it at some point. But as I mentioned before to properly talk about std::function I would kinda need to chat about type erasure and I’m not sure if I should or if I can do it in a simple enough way. Thinking about it anyway.