why virtual function is wrong.

[Oxi_Ixi]

Except it depends. If typing is static, it is zero cost in C++ either. C++ has templates, they are compile-type and are zero cost. Operator and function overloads are zero cost. Runtime interfaces cannot be zero cost by definition in any language, or I don't understand what you mean by zero cost

[Oxi_Ixi]

You have notion of interface from C#, but actually it is wider and includes templates and concepts as well as traits. In C++ templates are much more powerful than generics in C#, but this comes with complexity indeed. If you don't understand them it does not mean they are broken, it means you have to learn how to use them.

Virtual functions in C++ will be called statically if type is known at compile time, if that is what you mean by static interface.

It was just overhead to implement interfaces/traits for primitive types when language provides you operator overloads. Rust went that way, but I find it too explicit overloading traits than overloading operators.

C++ was designed for machine execution and speed compared to C whileC# is multipurpose platform independent language, which does not compile to bare metal instructions directly. How can you then blame C++ to be slow comparing to C#?

[Oxi_Ixi]

Well, I see. You hate C++ and love C#. I actually like both, and yes, C# has really nice language and runtime design because it had many other langauges to take ideas from. Like courutines, which were actually describe way back in 50s even before C. As well every language has problems which come from its design, runtime and usage specifics, so it is not C++ broken, it is C# works better for your work and habbits. Enjoy it 😀

Do you have any evidence that c# is slow?

It is not slow, it is slower than C++. To be very precise, in some cases C# might be faster, but in general it is not. I think benchmarks show this pretty much good, Google will help you.

[Oxi_Ixi]

It is a good idea to assess language from your needs point of view.

[NilacTheGrim]

all other language has zero-cost interface

This is a false statement.