std::generator

template<
    class Ref,
    class V = void,
    class Allocator = void
> class generator : public ranges::view_interface<generator<Ref, V, Allocator>>

namespace pmr {
template< class Ref, class V = void >
using generator =
    std::generator<Ref, V, std::pmr::polymorphic_allocator<>>;
}

A std::generator generates a sequence of elements by repeatedly resuming the coroutine from which it was returned. Each time a co_yield statement is evaluated, the coroutine produces one element of the sequence. When the co_yield statement is of the form co_yield ranges::elements_of(rng), each element of the range rng is successively produced as an element of the sequence.

std::generator models view and input_range.

The behavior of a program that adds a specialization for std::generator is undefined.

Data members

Internally, each active instance of std::generator is associated with a stack.

• When begin is called, a new stack is created and the generator is added to the stack.
• When co_yield ranges::elements_of(rng) is evaluated in a generator body, rng is converted to a generator and added to the stack that contains the enclosing generator.
• When a generator iterator is incremented, the coroutine at the top of the associated stack is resumed.
• When a generator finishes (i.e. when final_suspend is called), it is removed from the stack.

Template parameters

If Allocator is not void, then:

• std::allocator_traits<Allocator>::pointer is a pointer type;
• Allocator meets the Allocator requirements.

Member types

Let /*RRef*/ denote:

• std::remove_reference_t</*reference*/>&&, if /*reference*/ is a reference type, and
• /*reference*/ otherwise.

The following concepts are modeled:

• std::common_reference_with</*reference*/&&, /*value*/&>,
• std::common_reference_with</*reference*/&&, /*RRef*/&&>, and
• std::common_reference_with</*RRef*/&&, const /*value*/&>.

Member functions

Nested classes

Notes

Example

#include <generator>
#include <ranges>
#include <iostream>
 
std::generator<char> letters(char first)
{
    for (;; co_yield first++);
}
 
int main()
{
    for (const char ch : letters('a') | std::views::take(26))
        std::cout << ch << ' ';
    std::cout << '\n';
}

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See also