std::ranges::elements_of

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.

Template parameters

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

Data members

Member	Description
`[[no_unique_address]]` R range	a range (public member object)
`[[no_unique_address]]` Allocator allocator	an allocator. It has default member initializer that value-initializes itself (public member object)

Deduction guide

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

(since C++23)

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]

References

C++23 standard (ISO/IEC 14882:2024):

26.5.6 Class template elements_of [range.elementsof]

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