run_async.cpp

// The MIT License (MIT)
//
// Copyright (c) 2021 Mateusz Pusz
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
 
#include <mp-coro/async.h>
#include <mp-coro/sync_await.h>
#include <mp-coro/task.h>
#include <concepts>
#include <iostream>
#include <optional>
#include <syncstream>
 
mp_coro::task<int> foo() {
    const int res = co_await mp_coro::async([] { return 42; });
    co_await mp_coro::async([&] { std::cout << "Result: " << res << std::endl; });
    co_return res + 23;
}
 
mp_coro::task<> bar() {
    const auto res = co_await foo();
    std::cout << "Result of foo: " << res << std::endl;
}
 
mp_coro::task<int> boo() {
    const int res = co_await mp_coro::async([] {
        std::osyncstream(std::cout) << "About to throw an exception\n";
        throw std::runtime_error("Some error");
        std::osyncstream(std::cout) << "This will never be printed\n";
        return 42;
    });
    std::osyncstream(std::cout) << "I will never tell you that the result is: " << res << std::endl;
    co_return res;
}
 
mp_coro::task<> example() {
    co_await bar();
    co_await boo();
}
 
template <typename T>
void test(mp_coro::task<T> t) {
    try {
        if constexpr (std::is_void_v<T>)
            sync_await(t);
        else
            std::cout << "Result: " << sync_await(t) << '\n';
    } catch (const std::exception &ex) {
        std::cout << "Exception caught: " << ex.what() << "\n";
    }
}
 
int main() {
    try {
        test(example());
        test(boo());
        test(mp_coro::make_task(mp_coro::async([] { return 123; })));
    } catch (const std::exception &ex) {
        std::cout << "Unhandled exception: " << ex.what() << "\n";
    }
}