cpp11_coroutine.cc

/**
 * C++11 coroutine example using Boost.Coroutine
 * Created by daeyun on 1/13/15.
 */
#include <iostream>
#include <boost/coroutine/all.hpp>

template <typename T>
using coro = boost::coroutines::asymmetric_coroutine<T>;
using std::cout;
using std::endl;

struct FibState {
  FibState() { cout << "FibState()" << endl; }
  ~FibState() { cout << "~FibState()" << endl; }
  int prev[2]{1, 0};
  int current;
};

int main() {
  coro<int>::pull_type source([&](coro<int>::push_type& sink) {
    FibState fib;
    while (true) {
      fib.current = fib.prev[0] + fib.prev[1];
      cout << "(generating " << fib.current << "..)" << endl;

      // Similar to `yield` in Python
      sink(fib.current);

      fib.prev[0] = fib.prev[1];
      fib.prev[1] = fib.current;
    }
    cout << "Not printed" << endl;
  });

  const int kFibLimit = 100;

  cout << "Fibonacci numbers less than " << kFibLimit << ":" << endl;
  for (auto i : source) {
    if (i > kFibLimit) break;
    cout << i << endl;
  }

  cout << "End of main()" << endl;
  return 0;
}

/* Output:
FibState()
(generating 1..)
Fibonacci numbers less than 100:
1
(generating 1..)
1
(generating 2..)
2
(generating 3..)
3
(generating 5..)
5
(generating 8..)
8
(generating 13..)
13
(generating 21..)
21
(generating 34..)
34
(generating 55..)
55
(generating 89..)
89
(generating 144..)
End of main()
~FibState()
 */