advance_with_begin.cpp

Shows how to (ab)use begin() to advance the iterator.

#include <iostream>
#include <utility>
 
#include "async_generator.h"
#include "eager_task.h"
#include "generator.h"
#include "sync_generator_adapter.h"
#include "task.h"
 
namespace {
 
wwa::coro::task<int> get_next_value(int n)
{
    co_return n + 1;
}
 
wwa::coro::async_generator<int> async_first_n(int n)
{
    int v = 0;
    while (v < n) {
        co_yield v;
        v = co_await get_next_value(v);
    }
}
 
wwa::coro::generator<int> sync_first_n(int n)
{
    int v = 0;
    while (v < n) {
        co_yield v;
        ++v;
    }
}
 
wwa::coro::eager_task iterate_over_async()
{
    auto gen = async_first_n(5);
    auto it  = co_await gen.begin();
    auto end = gen.end();
 
    do {
        std::cout << *it << " ";
    } while (co_await gen.begin() != end);
 
    std::cout << "\n";
}
 
void iterate_over_sync()
{
    auto gen = sync_first_n(5);
    auto it  = gen.begin();
    auto end = gen.end();
 
    do {
        std::cout << *it << " ";
    } while (gen.begin() != end);
 
    std::cout << "\n";
}
 
void iterate_over_adapted_async()
{
    auto async = async_first_n(5);
    auto gen   = wwa::coro::sync_generator_adapter(std::move(async));
    auto it    = gen.begin();
    auto end   = gen.end();
 
    do {
        std::cout << *it << " ";
    } while (gen.begin() != end);
 
    std::cout << "\n";
}
 
}  // namespace
 
int main()
{
    std::cout << "Iterating over asynchronous generator:\n";
    iterate_over_async();
    std::cout << "Iterating over synchronous generator:\n";
    iterate_over_sync();
    std::cout << "Iterating over adapted asynchronous generator:\n";
    iterate_over_adapted_async();
 
    // Expected output:
    // Iterating over asynchronous generator:
    // 0 1 2 3 4
    // Iterating over synchronous generator:
    // 0 1 2 3 4
    // Iterating over adapted asynchronous generator:
    // 0 1 2 3 4
 
    return 0;
}