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execute true

What It Does

std::generator<T> is a coroutine type for lazy sequence generation. Each co_yield expression suspends the coroutine, resuming when the next element is requested. Elements are produced incrementally during iteration.

Why It Matters

Container allocation is avoided for sequential data access. Memory consumption is bounded by a single element, the type is compatible with range adaptors, and unbounded sequences can be expressed without resource exhaustion.

Example

#include <generator>
#include <print>

std::generator<int> fibonacci(int limit) {
    auto a = 0;
    auto b = 1;

    while (a < limit) {
        co_yield a;
        auto next = a + b;
        a = b;
        b = next;
    }
}

std::generator<int> iota(int start = 0) {
    while (true) {
        co_yield start++;
    }
}

int main() {
    std::println("fib:");
    for (auto n : fibonacci(100)) {
        std::println("{}", n);
    }

    // Take first 5 from infinite sequence
    std::println("first 5, starting with 10:");
    for (auto n : iota(10) | std::views::take(5)) {
        std::println("{}", n);
    }
}