Différences

Ci-dessous, les différences entre deux révisions de la page.

--- lang:cpp:coroutine [2020/03/26 15:19] – Ajout de co_yield pour gcc et clang root
+++ lang:cpp:coroutine [2023/04/27 05:05] (Version actuelle) – Ajout de "Gajendra Gulgulia" root
@@ Ligne 1: / Ligne 1: @@
+====Exemples====
 ===co_yield===
 Version Visual Studio :
@@ Ligne 184: / Ligne 185: @@
  Only after resumed !
 </code>
+====Tutorial====
+===Gajendra Gulgulia===
+[[https://ggulgulia.medium.com/painless-c-coroutines-part-1-ba90dd101adb|Painless C++ Coroutines-Part 1]] {{ :lang:cpp:coroutine:painless_c_coroutines_-part_1._learn_how_to_cretae_a_simple_coroutine_by_gajendra_gulgulia_may_2021_medium_medium_2023-02-25_11_53_43_.html |Archive du 31/05/2021 le 25/02/2023}}
+  * Partie 4
+<code cpp>
+#include <coroutine>
+#include <iostream>
+//global counter
+int num{0};
+struct ReturnObject{
+  struct promise_type{
+    promise_type(){std::cout <<  num++ << ". promise_type default ctor\n";}
+    ReturnObject get_return_object() {
+        std::cout <<  num++ << ". promise_type::get_return_object\n";
+        return {};
+    }
+    std::suspend_never initial_suspend() {
+         std::cout <<  num++ << ". promise_type::initial_suspend\n";
+         return {};
+    }
+    std::suspend_never final_suspend() noexcept{
+        std::cout <<  num++ << ". promise_type::final_suspend\n";
+        return {};
+    }
+    void unhandled_exception(){std::cout <<  num++ << ".throw\n";}
+  };
+};
+ReturnObject foo(){
+    std::cout <<  num++ << ".  hello from coroutine1\n";
+    co_await std::suspend_never{}; //never suspend the coroutine at this point
+    co_await std::suspend_never{}; //never suspend the coroutine at this point
+    co_await std::suspend_always{}; //suspend the coroutine at this point
+    std::cout <<  num++ << ".  hello from coroutine2\n";
+}
+int main(){foo();
+        std::cout <<  num++ << ". END\n";
+}
+</code>
+  * Partie 5
+[[https://ggulgulia.medium.com/painless-coroutines-part2-29b36008b507|Painless C++ Coroutines-Part 2]] {{ :lang:cpp:coroutine:painless_c_coroutines-part_2._as_promised_i_continue_the_journey_of_by_gajendra_gulgulia_medium_2023-02-25_11_53_45_.html |Archive du 31/05/2021 le 25/02/2023}}
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+static int ctr{0};
+struct ReturnObject {
+    struct promise_type {
+        ReturnObject get_return_object() {
+            // call ctor of ReturnObject with the coroutine handle
+            return {
+                std::coroutine_handle<promise_type>::from_promise(*this)};  // A
+        }
+        std::suspend_never initial_suspend() { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        void unhandled_exception() {}
+    };
+    // B.3 implicit conversion operator
+    operator std::coroutine_handle<>() const { return h_; }
+   private:
+    std::coroutine_handle<> h_;  // B.1: member variable
+    ReturnObject(std::coroutine_handle<> h) : h_{h} {}  // B.2: ctor
+};
+// coroutine
+ReturnObject foo() {
+    std::cout << ++ctr << ". hello from coroutine 1\n";
+    co_await std::suspend_always{};  // suspend the coroutine at this point
+    std::cout << ++ctr << ". hello from coroutine 2\n";
+    co_await std::suspend_always{};  // suspend the coroutine at this point
+    std::cout << ++ctr << ". hello from coroutine 3\n";
+}
+// main
+int main() {
+    std::coroutine_handle<> h = foo();
+    std::cout << ++ctr << ". resuming coroutine from main 1\n";
+    h();
+    std::cout << ++ctr << ". resuming coroutine from main 2\n";
+    h.resume();  // same as h()
+}
+</code>
+  * Partie 6.2
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+int ctr{0};
+struct suspend_always {
+    bool await_ready() const noexcept {
+        std::cout << ++ctr << ". suspend_always::await_ready\n";
+        return false;
+    }
+    void await_suspend(std::coroutine_handle<> h) const noexcept {
+        std::cout << ++ctr << ". suspend_always::await_suspend\n";
+    }
+    void await_resume() const noexcept {
+        std::cout << ++ctr << ". suspend_always::await_resume\n";
+    }
+};
+// ReturnObject same as in section 5
+struct ReturnObject {
+    struct promise_type {
+        unsigned value_{0};
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() noexcept { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        void unhandled_exception() {}
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<>() const { return h_; }
+};
+ReturnObject foo() {
+    std::cout << ++ctr << ". first hello from coroutine\n";
+    co_await suspend_always{};  // evaluate custom awaiter
+    std::cout << ++ctr << ". second hello from coroutine\n";
+}
+int main() {
+    std::coroutine_handle<> h = foo();
+    std::cout << ++ctr << ". main\n";
+    h();
+}
+</code>
+  * Partie 6.3
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+int ctr{0};
+struct suspend_always {
+    bool await_ready() const noexcept {
+        std::cout << ++ctr << ". suspend_always::await_ready\n";
+        return false;
+    }
+    bool await_suspend(std::coroutine_handle<> h) const noexcept {
+        std::cout << ++ctr << ". suspend_always::await_suspend\n";
+        return true;  // Change it.
+    }
+    void await_resume() const noexcept {
+        std::cout << ++ctr << ". suspend_always::await_resume\n";
+    }
+};
+struct ReturnObject {
+    struct promise_type {
+        unsigned value_{0};
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        void unhandled_exception() {}
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<>() const { return h_; }
+};
+ReturnObject foo() {
+    std::cout << ++ctr << ". first hello from coroutine\n";
+    co_await suspend_always{};  // evaluate custom awaiter
+    std::cout << ++ctr << ". second hello from coroutine\n";
+    co_await std::suspend_always{};
+    std::cout << ++ctr << ". third hello from coroutine\n";
+}
+int main() { std::coroutine_handle<> h = foo(); }
+</code>
+  * Partie 6.4
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+int ctr{0};
+// ReturnObject same as in section 5
+struct ReturnObject {
+    struct promise_type {
+        unsigned value_{0};
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() {
+            std::cout << ++ctr << ". promise_type::initial_suspend\n";
+            return {};
+        }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        void unhandled_exception() {}
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<>() const { return h_; }
+};
+struct suspend_always {
+    bool await_ready() const noexcept {
+        std::cout << ++ctr << ". suspend_always::await_ready\n";
+        return false;
+    }
+    void await_suspend(
+        std::coroutine_handle<ReturnObject::promise_type> h) const noexcept {
+        std::cout << ++ctr << ". suspend_always::await_suspend\n";
+    }
+    void await_resume() const noexcept {
+        std::cout << ++ctr << ". suspend_always::await_resume\n";
+    }
+};
+ReturnObject foo() {
+    std::cout << ++ctr << ". first hello from coroutine\n";
+    co_await suspend_always{};  // evaluate custom awaiter
+    std::cout << ++ctr << ". second hello from coroutine\n";
+}
+int main() {
+    std::coroutine_handle<> h = foo();
+    std::cout << ++ctr << ". resuming coroutinefrom main\n";
+    h();
+}
+</code>
+  * Partie 6.5
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+int ctr{0};
+template <typename PromiseType = void>  // note this
+struct suspend_always {
+    bool await_ready() const noexcept {
+        std::cout << ++ctr << ". suspend_always::await_ready\n";
+        return false;
+    }
+    /*********** and this **********/
+    void await_suspend(std::coroutine_handle<PromiseType> h) const noexcept {
+        std::cout << ++ctr << ". suspend_always::await_suspend\n";
+    }
+    void await_resume() const noexcept {
+        std::cout << ++ctr << ". suspend_always::await_resume\n";
+    }
+};
+// same as in section 5
+struct ReturnObject {
+    struct promise_type {
+        unsigned value_{0};
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        void unhandled_exception() {}
+    };
+    std::coroutine_handle<> h_;
+    ReturnObject(std::coroutine_handle<> h) : h_{h} {}
+    operator std::coroutine_handle<>() const { return h_; }
+};
+ReturnObject foo() {
+    std::cout << ++ctr << ". first hello from coroutine\n";
+    co_await suspend_always<>{};  // note this
+    co_await suspend_always<ReturnObject::promise_type>{};
+    std::cout << ++ctr << ". second hello from coroutine\n";
+}
+int main() {
+    std::coroutine_handle<> h = foo();
+    std::cout << ++ctr << ". resuming coroutine from main 1\n";
+    h();
+    std::cout << ++ctr << ". resuming coroutine from main 2\n";
+    h();
+}
+</code>
+[[https://ggulgulia.medium.com/painless-c-coroutine-part-3-536e4bce4f4f|Painless C++ Coroutine-Part 3]] {{ :lang:cpp:coroutine:painless_c_coroutines-part_3._in_first_part_of_the_issue_painless_by_gajendra_gulgulia_medium_2023-02-25_11_53_46_.html |Archive du 31/05/2021 le 25/02/2023}}
+  * Partie 7.1
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+#include <memory>
+// custom suspend_never
+struct suspend_never {
+    double* val_{new double(10.234)};
+    bool await_ready() const noexcept { return true; }
+    void await_suspend(std::coroutine_handle<> h) const noexcept {}
+    double* await_resume() const noexcept { return val_; }
+};
+// ReturnObject
+struct ReturnObject {
+    struct promise_type {
+        unsigned value_{0};
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        void unhandled_exception() {}
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<>() const { return h_; }
+};
+// coroutine
+ReturnObject foo() {
+    // temporary suspend_never is destroyed after evaluation
+    auto val1 = co_await suspend_never{};
+    std::cout << *val1 << "\n";  //(1)
+    *val1 = 20.234;
+    delete val1;
+    auto val2 = co_await suspend_never{};
+    std::cout << *val2 << "\n";  //(2) == (1)
+    delete val2;
+}
+// main
+int main() { std::coroutine_handle<> h = foo(); }
+</code>
+  * Partie 7.2
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+int ctr{0};
+template <typename PromiseType = void>  // 1
+struct suspend_never {
+    PromiseType* promise_{nullptr};  // 2.a
+    bool await_ready() const noexcept { return false; }
+    void await_suspend(std::coroutine_handle<PromiseType> h) noexcept {
+        promise_ = &h.promise();  // 2.b
+    }
+    PromiseType* await_resume() const noexcept { return promise_; }  // 2.c
+};
+struct ReturnObject {
+    struct promise_type {
+        int val_{11}; /*<---------------------- Note this  */
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        void unhandled_exception() {}
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<>() const { return h_; }
+};
+ReturnObject foo() {
+    auto promise =
+        co_await suspend_never<ReturnObject::promise_type>{};  // 1, 2.d
+    std::cout << promise->val_ << "\n";
+}
+int main() {
+    std::coroutine_handle<> h = foo();
+    h();
+}
+</code>
+  * Partie 7.3
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+int ctr{0};
+template <typename PromiseType = void>  // 1
+struct suspend_never {
+    PromiseType* promise_{nullptr};  // 2.a
+    bool await_ready() const noexcept { return false; }
+    void await_suspend(std::coroutine_handle<PromiseType> h) noexcept {
+        promise_ = &h.promise();  // 2.b
+    }
+    PromiseType* await_resume() const noexcept { return promise_; }  // 2.c
+};
+struct ReturnObject {
+    struct promise_type {
+        int val_{11}; /*<------------- Note this  */
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        void unhandled_exception() {}
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<promise_type>() const { return h_; }
+};
+ReturnObject foo() {
+    auto promise =
+        co_await suspend_never<ReturnObject::promise_type>{};  // 1, 2.d
+    std::cout << "From coroutine " << promise->val_ << "\n";
+}
+int main() {
+    std::coroutine_handle<ReturnObject::promise_type> h = foo();
+    ReturnObject::promise_type prom = h.promise();
+    std::cout << "From main: " << prom.val_ << "\n";
+    h();
+}
+</code>
+  * Partie 7.4
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+#include <thread>
+int ctr{0};
+template <typename PromiseType = void>
+struct suspend_never {
+    PromiseType* promise_{nullptr};
+    bool await_ready() const noexcept { return false; }  //
+    bool await_suspend(std::coroutine_handle<PromiseType> h) noexcept {
+        promise_ = &h.promise();
+        std::cout << ctr++ << ". In suspend_always::await_suspend\n"
+                  << "   Do further processing on promise_->_val = "
+                  << promise_->val_ << " ... \n";
+        return false;
+    }
+    PromiseType* await_resume() const noexcept { return promise_; }
+};
+struct ReturnObject {
+    struct promise_type {
+        int val_;
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        void unhandled_exception() {}
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<promise_type>() const { return h_; }
+};
+using PromType = ReturnObject::promise_type;
+ReturnObject foo() {
+    std::cout
+        << ctr++
+        << ". Suspending the coroutine for 1st time with trivial awaitable\n";
+    co_await std::suspend_always{};
+    std::cout
+        << ctr++
+        << ". Suspending the coroutine for 2nd time with custom awaitable\n";
+    auto promise = co_await suspend_never<PromType>{};
+    std::cout << ctr++ << ". Coroutine finished\n";
+}
+int main() {
+    std::coroutine_handle<PromType> h = foo();
+    PromType* prom = &h.promise();
+    std::cout << ctr++
+              << ". From main: current value of promise_->val_: " << prom->val_
+              << "\n";  // access promise.val_ in main
+    std::cout << ctr++
+              << ". Changing  promise_->val_ in main and resuming coroutine\n";
+    prom->val_ = 21;
+    h();
+    std::cout << ctr++ << ". main finished\n";
+}
+</code>
+  * Partie 8
+KO :
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+int ctr{0};
+template <typename PromiseType = void>  // 1
+struct suspend_always {
+    PromiseType* promise_{nullptr};  // 2.a
+    bool await_ready() const noexcept { return false; }
+    void await_suspend(std::coroutine_handle<PromiseType> h) noexcept {
+        promise_ = &h.promise();  // 2.b
+    }
+    PromiseType* await_resume() const noexcept { return promise_; }  // 2.c
+};
+struct ReturnObject {
+    struct promise_type {
+        int val_; /*<---------------------------------------------- Note this */
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        void unhandled_exception() {}
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<promise_type>() const { return h_; }
+};
+using PromType = ReturnObject::promise_type;
+ReturnObject generator() {
+    auto promise = co_await suspend_always<PromType>{};
+    for (int i = 0;; i++) {
+        promise->val_ = i;
+        co_await std::suspend_always{};
+    }
+}
+int main() {
+    std::coroutine_handle<PromType> h = generator();
+    PromType& prom = h.promise();
+    for (int i = 0; i < 5; ++i) {
+        std::cout << "From main: " << prom.val_ << "\n";
+        h();
+    }
+}
+</code>
+OK :
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+template <typename PromiseType = void>
+struct suspend_never {
+    PromiseType* promise_{nullptr};
+    bool await_ready() const noexcept { return false; }
+    bool await_suspend(std::coroutine_handle<PromiseType> h) noexcept {
+        promise_ = &h.promise();
+        return false;
+    }
+    PromiseType* await_resume() const noexcept { return promise_; }
+};
+struct ReturnObject {
+    struct promise_type {
+        int val_;
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        void unhandled_exception() {}
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<promise_type>() const { return h_; }
+};
+using PromType = ReturnObject::promise_type;
+ReturnObject generator() {
+    auto promise = co_await suspend_never<PromType>{};
+    for (int i = 0;; i++) {
+        promise->val_ = i;
+        co_await std::suspend_always{};
+    }
+}
+ReturnObject evenNumberGenerator() {
+    auto promise = co_await suspend_never<PromType>{};
+    for (int i = 0;; i = i + 2) {
+        promise->val_ = i;
+        co_await std::suspend_always{};
+    }
+}
+ReturnObject oddNumberGenerator() {
+    auto promise = co_await suspend_never<PromType>{};
+    for (int i = 1;; i = i + 2) {
+        promise->val_ = i;
+        co_await std::suspend_always{};
+    }
+}
+int main() {
+    std::coroutine_handle<PromType> h = generator();
+    PromType& prom = h.promise();
+    for (int i = 0; i < 5; ++i) {
+        std::cout << "From main: " << prom.val_ << "\n";
+        h();
+    }
+}
+</code>
+[[https://ggulgulia.medium.com/painless-c-coroutines-part-4-69117214bfdc|Painless C++ Coroutines-Part 4]] {{ :lang:cpp:coroutine:painless_c_coroutines-part_4._in_part_one_two_and_three_of_the_by_gajendra_gulgulia_medium_2023-02-25_11_53_48_.html |Archive du 13/06/2021 le 25/02/2023
+}}
+  * Partie 9
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+struct ReturnObject {
+    struct promise_type {
+        int val_;
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() noexcept { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        std::suspend_always yield_value(int value) {
+            val_ = value;
+            return {};
+        }
+        void unhandled_exception() {}
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<promise_type>() const { return h_; }
+};
+using PromType = ReturnObject::promise_type;
+ReturnObject generator() {
+    for (int i = 0;; i++) {
+        co_yield i;
+    }
+}
+int main() {
+    std::coroutine_handle<PromType> h = generator();
+    PromType& prom = h.promise();
+    for (int i = 0; i < 5; ++i) {
+        std::cout << "From main: " << prom.val_ << "\n";
+        h();
+    }
+}
+ReturnObject evenNumberGenerator() {
+    for (int i = 0;; i = i + 2) {
+        co_yield i;
+    }
+}
+ReturnObject oddNumberGenerator() {
+    for (int i = 1;; i = i + 2) {
+        co_yield i;
+    }
+}
+</code>
+  * Partie 10
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+template <typename T>
+struct ReturnObject {
+    struct promise_type {
+        T val_;
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() noexcept { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        std::suspend_always yield_value(T value) {
+            val_ = value;
+            return {};
+        }
+        void unhandled_exception() {}
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<promise_type>() const { return h_; }
+};
+using PromType = ReturnObject<float>::promise_type;
+template <typename T>
+ReturnObject<T> generator() {
+    for (int i = 0;; i++) {
+        co_yield 1.234 + static_cast<T>(i);
+    }
+}
+int main() {
+    std::coroutine_handle<PromType> h = generator<float>();
+    PromType& prom = h.promise();
+    for (int i = 0; i < 5; ++i) {
+        std::cout << "From main: " << prom.val_ << "\n";
+        h();
+    }
+}
+</code>
+[[https://ggulgulia.medium.com/painless-c-coroutines-part-5-f28e74c58a2c|Painless C++ Coroutines-Part 5]] {{ :lang:cpp:coroutine:painless_c_coroutines-part_5._in_the_fifth_issue_of_the_tutorial_by_gajendra_gulgulia_medium_2023-02-25_11_53_49_.html |Archive du 13/06/2021 le 25/02/2023}}
+  * Partie 11.1
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+struct ReturnObject {
+    struct promise_type {
+        int val_{23};
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() noexcept { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        void unhandled_exception() {}
+        void return_void() {}
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<promise_type>() const { return h_; }
+};
+using PromType = ReturnObject::promise_type;
+ReturnObject foo() { co_return; }
+int main() {
+    std::coroutine_handle<PromType> h = foo();
+    std::cout << h.promise().val_ << "\n";
+}
+</code>
+  * Partie 11.2
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+struct ReturnObject {
+    struct promise_type {
+        int val_;
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() noexcept { return {}; }
+        std::suspend_never final_suspend() noexcept { return {}; }
+        void unhandled_exception() {}
+        void return_value(int val) { val_ = val; }
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<promise_type>() const { return h_; }
+};
+using PromType = ReturnObject::promise_type;
+ReturnObject foo() { co_return 121; }
+int main() {
+    std::coroutine_handle<PromType> h = foo();
+    std::cout << h.promise().val_ << "\n";
+}
+</code>
+  * Partie 12
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+struct ReturnObject {
+    struct promise_type {
+        int val_;
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() noexcept { return {}; }
+        void return_void() { std::cout << "called return_void\n"; }
+        std::suspend_always final_suspend() noexcept { return {}; }
+        void unhandled_exception() {}
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<promise_type>() const { return h_; }
+};
+ReturnObject foo() { co_await std::suspend_never{}; }
+int main() { foo(); }
+</code>
+<code cpp>
+#include <concepts>
+#include <coroutine>
+#include <exception>
+#include <iostream>
+struct ReturnObject {
+    struct promise_type {
+        int val_;
+        ReturnObject get_return_object() {
+            return {std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_never initial_suspend() noexcept { return {}; }
+        std::suspend_always final_suspend() noexcept {
+            std::cout << "suspending coroutine for one last time\n";
+            return {};
+        }
+        void unhandled_exception() {}
+        void return_void() { std::cout << "return_void\n"; }
+    };
+    std::coroutine_handle<promise_type> h_;
+    ReturnObject(std::coroutine_handle<promise_type> h) : h_{h} {}
+    operator std::coroutine_handle<promise_type>() const { return h_; }
+};
+using PromType = ReturnObject::promise_type;
+ReturnObject foo() { co_await std::suspend_never{}; }
+int main() {
+    std::coroutine_handle<PromType> h = foo();
+    PromType* prom = &h.promise();
+    /*
+     call h.resume() many times
+    */
+    if (h.done()) {
+        /*
+          do something with prom one last time
+        */
+        std::cout << "done execution of coroutine\n";
+        h.destroy();
+    }
+}
+</code>