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Even if they're a good general design, half the uses of SFINAE are absolutely insane and from what I understand it's significantly harder than it should be to make a fully generic template across all kinds of edge case and corner case types.

The attitude with templates seems to be that if something is at all possible with hacks then there doesn't need to be any language support added, even if it would be vastly simpler to read and write and probably to compile. I don't think that works out well.

I wouldn't call myself a c++ expert but I have used the language for a long time. In my opinion, templates have a lot of awesome uses outside of SFINAE and if you find yourself reaching for SFINAE, that's probably code smell and you can probably simplify the design elsewhere to avoid it.

Generally I find the best use of templates is the most basic: you want to write some code that operates on duck-types. As long as one is able to control themselves and pick the right use cases for maintainability, templates are simple enough. In my experience, this is very doable.

Concepts are also a really cool way to rein in which types are accepted as a template parameter and have a lot of potential to make templates easier to understand and teach. To me, this is the most exciting c++20 feature.

With C++17, if constexpr removed most of the necessity for crazy SFINAE uses. Before that it was definitely worse. C++20 adds even more to make things more "semantic"; they're constantly adding better language support for templates.

No one disputes that meta programming is useful. What is disputed is C++ templates being a "good" way to meta program.

I certainly understand metaprogramming, but navigating very dense C++ templates is one of the most complicated things I've had to do in my life. One or two levels of abstraction and you will lose your ability to hold everything you need to solve a problem in your head, and after a few dozen lines the source code is unreadable.

> You need to understand the core language and the template language to be effective with them.

this is a bug.

I guess that just hasn't been my experience at all. I don't think a nested C++ template is any more complicated than a CL macro with a corresponding level of nested `.

I also don't really see how requiring understanding of a language to generate that language could be considered a bug - every macro system carries that requirement. C++ just happens to be (much) more complex than most languages (and I do agree that a large amount of that complexity is probably not necessary).

I'd argue it's significantly more complex because you don't have access to the C++ AST, templates are ultimately non-hygienic macros, their results are invisible to both developer and user, and potential errors are inscrutable. They're difficult to abstract over, and you will wind up repeating yourself quite often since you can't just write normal C++ code with C++ includes for helper functions and data structures.

I should be more clear about what I meant on the bug. C++ templates force you to understand the entirety of the language at once and hack around its edges because it doesn't support actual meta programming. It's hard for me to come up with a concrete example, but my experience writing some advanced compile-time evaluation with SFINAE patterns left me forgetting how things worked within minutes of typing them. Compare to say Rust, where the generics implementation is much cleaner and macro system better flushed out and easier to read/understand. Or the LISPs where your macro is just more LISP code.

And not for nothing, templates destroy compile times. They take a long time to write and edit and make everyone else using them work slower. All told, templates do not make it easier to write C++ except in trivial cases and first-order abstractions.

The kind of stuff you are able to do with entt (https://github.com/skypjack/entt#code-example) like `entities.view<Position, Sprite>.each([&](auto &pos, auto &vel) { ... });` is super awesome IMO. And then it compiles down to just directly inlined straight walks over the respective arrays (looking in godbolt.org). It's basically almost optimal for it.

I do agree that you can go insane with templates and have a bad time. You just have to choose well. However if you have a problem with there existing other problematic code in the same language (that may be separate from your code), then C++ is maybe not the best fit. There's a lot of C++ out there.

Any recommendation for books/blogs/videos/code to learn about this ?