CPP Modern C++ Features (C++17/20) 4

Question 1

In C++20 Concepts, what does `template requires std::integral` enforce?

Accepted Answer

T must satisfy the std::integral concept at compile time

Answer

The requires clause constrains the template, producing a clear diagnostic if the type does not satisfy std::integral.

Question 2

Which C++20 feature allows `auto add(auto a, auto b)` as shorthand for a function template?

Accepted Answer

Abbreviated function templates

Answer

C++20 abbreviated function templates use auto in parameter position to implicitly declare a template parameter for each auto.

Question 3

What keyword makes a C++20 function a coroutine when it appears in the function body?

Accepted Answer

co_await, co_yield, or co_return

Answer

Any function containing co_await, co_yield, or co_return is a coroutine in C++20; no special return-type keyword is needed.

Question 4

What does the C++20 Ranges `std::views::filter` return?

Accepted Answer

A lazy view that skips elements not satisfying the predicate

Answer

std::views::filter returns a range adaptor view that lazily filters elements without allocating a new container.

Question 5

In C++20, `std::span<int>` differs from `int*` in that:

Accepted Answer

It carries both a pointer and a size, providing bounds information

Answer

std::span is a non-owning view over a contiguous sequence, pairing a pointer with an extent (size) for safe access.

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