The following code example is taken from the book
C++23 - The Complete Guide
by Nicolai M. Josuttis,
Leanpub, 2026
The code is licensed under a
Creative Commons Attribution 4.0 International License.
// raw code
#include <utility>
#include <generator>
std::generator<long> fibonacci(int num)
{
// first two numbers are 1:
long a = 1;
long b = 1;
co_yield a; // SUSPEND with first number
co_yield b; // SUSPEND with second number
// loop over the remaining num-2 sums of previous two numbers:
for (int i = 2; i < num; ++i) {
auto sum = a + b;
co_yield sum; // SUSPEND with sum of previous two numbers
a = std::exchange(b, sum);
}
}