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std::ranges::elements_of

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< cpp‎ | ranges
 
 
Ranges library
Range access
Range conversions
(C++23)

Range primitives
elements_of
(C++23)



Dangling iterator handling
Range concepts
Views

Range factories
Range adaptors
Range generators
Range adaptor objects
Range adaptor closure objects
Helper items
(until C++23)(C++23)


 
Defined in header <ranges>
template< ranges::range R, class Allocator = std::allocator<std::byte> >
struct elements_of;
(since C++23)

Encapsulates a range. Specializations of elements_of act as a tag in overload sets to disambiguate when a range should be treated as a sequence rather than a single value.

Contents

[edit] Template parameters

R - a type that satisfies range
Allocator - an allocator type that meets the requirements of Allocator

[edit] Data members

Member name Definition
range
a range of type R
(public member object)
allocator
an allocator of type Allocator. It has default member initializer that value initializes itself
(public member object)

All these members are declared with [[no_unique_address]] attribute.

[edit] Deduction guide

template< class R, class Allocator = std::allocator<std::byte> >
elements_of( R&&, Allocator = Allocator() ) -> elements_of<R&&, Allocator>;
(since C++23)

[edit] Example

#include <any>
#include <generator>
#include <iostream>
#include <ranges>
#include <string_view>
 
template<bool Elementwise>
std::generator<std::any> gen(std::ranges::input_range auto&& r)
{
    if constexpr (Elementwise)
        co_yield std::ranges::elements_of(r); // yield each element of r
    else
        co_yield r;                           // yield r as a single value
}
 
int main()
{
    auto test = std::string_view{"test"};
 
    for (std::any a : gen<true>(test))
        std::cout << '[' << std::any_cast<char>(a) << "] ";
    std::cout << '\n';
 
    for (std::any a : gen<false>(test))
        std::cout << '[' << std::any_cast<std::string_view>(a) << "] ";
    std::cout << '\n';
}

Output:

[t] [e] [s] [t] 
[test]

[edit] References

  • C++23 standard (ISO/IEC 14882:2024):
  • 26.5.6 Class template elements_of [range.elementsof]