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std::ranges::views::all, std::ranges::all_view

From cppreference.com
< cpp‎ | ranges
 
 
 
template <ranges::viewable_range R>
using all_view = decltype(views::all(std::declval<R>()));
(1) (since C++20)
namespace views {

    inline constexpr /*unspecified*/ all = /*unspecified*/;

}
(2) (since C++20)

A range adaptor that returns a view that includes all elements of its range argument.

The expression views::all(E) is expression-equivalent (has the same effect) to:

  • decay-copy(E) if the decayed type of E models view.
  • Otherwise, std::ranges::ref_view{E} if that expression is well-formed
  • Otherwise, std::ranges::subrange{E}

[edit] Expression-equivalent

Expression e is expression-equivalent to expression f, if e and f have the same effects, either are both potentially-throwing or are both not potentially-throwing (i.e. noexcept(e) == noexcept(f)), and either are both constant subexpressions or are both not constant subexpressions.

[edit] Example

#include <ranges>
#include <vector>
#include <iostream>
 
int main()
{
    std::vector<int> v{0,1,2,3,4,5};
    for(int n : std::views::all(v) | std::views::take(2) ) {
        std::cout << n << ' ';
    }
}

Output:

0 1