coro/coroexcept.cpp

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 <iostream>
#include <exception>
#include <generator>

std::generator<int> coro()
{
  std::cout << "\t** coro(): yield 1" << std::endl;
  co_yield 1;                                       // SUSPEND with 1

  std::cout << "\t** coro(): yield 2" << std::endl;
  co_yield 2;                                       // SUSPEND with 2

  std::cout << "\t** coro(): THROW" << std::endl;
  throw std::runtime_error{"error in coroutine"};   // EXCEPTION
  
  std::cout << "\t** coro(): not reached" << std::endl;
}

int main()
{
  auto gen = coro();

  std::cout << "begin(): " << std::endl;
  auto pos = gen.begin();                           // START coroutine

  while (pos != gen.end()) {
    std::cout << "got: " << *pos << std::endl;
    std::cout << "++pos: " << std::endl;
    try {
      ++pos;                                        // RESUME coroutine
    }
    catch (const std::exception& e) {
      std::cout << "EXCEPTION: " << e.what() << std::endl;
    }
  }
  std::cout << "at end()" << std::endl;
}