std::generator (C++23)

One-Liner

A coroutine generator that lazily produces a sequence of values with co_yield — it replaces hand-written iterators, allocates nothing on the heap (the allocator is customizable), and cuts the amount of code by an order of magnitude.

Header

#include <generator>

Core API Cheat Sheet

Operation	Signature	Description
Generator type	template<class T> class generator	Lazy sequence of values; satisfies the view concept
Yield a value	co_yield expr;	Produces a value and suspends
Finish generating	co_return;	Ends the generator
Iteration	generator::iterator	Input iterator, for range-for loops
Range adaptation	Usable directly in ranges:: pipelines	A generator is a view, so it composes
Reference type	generator<const T&>	Yields by reference (avoids copies)
Allocator	template<class T, class Alloc> class generator	Customizable allocator for the coroutine frame

Minimal Example

// Standard: C++23
#include <generator>
#include <iostream>

std::generator<int> fibonacci() {
    int a = 0, b = 1;
    while (true) {
        co_yield a;
        auto tmp = a;
        a = b;
        b = tmp + b;
    }
}

int main() {
    for (int v : fibonacci() | std::views::take(8)) {
        std::cout << v << " "; // 0 1 1 2 3 5 8 13
    }
}

Embedded Applicability: Moderate

• Lazy evaluation: the next value is computed only when needed, with no memory pre-allocated for the whole sequence
• The coroutine frame can use a custom allocator, which suits static memory pools
• Replaces hand-written iterators and callbacks, a big readability win
• C++23 feature; compiler support is still rolling out (GCC 14+, Clang 17+, MSVC 19.34+)
• Watch the generator's lifetime: accessing a yielded value after the generator is destroyed is undefined behavior

Compiler Support

GCC	Clang	MSVC
14	17	19.34

See Also

• cppreference: std::generator

---

Some content is referenced from cppreference.com and used under the CC-BY-SA 4.0 license