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July 9, 2021 08:16
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PHP 中 yield：嵌套展平 yield 表达式
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| function stackedCoroutine(\Generator $gen) | |
| { | |
| $stack = new \SplStack; | |
| $exception = null; | |
| for (;;) { | |
| try { | |
| if ($exception) { | |
| $gen->throw($exception); | |
| $exception = null; | |
| continue; | |
| } | |
| // 执行一次 yield | |
| $value = $gen->current(); | |
| if ($value instanceof \Generator) { | |
| // 压入当前的 $gen, 先把嵌套的 $gen 执行 | |
| $stack->push($gen); | |
| $gen = $value; | |
| continue; | |
| } | |
| // 当前的 gen 函数是否执行完毕了 | |
| $isReturnValue = $value instanceof CoroutineReturnValue; | |
| if (!$gen->valid() || $isReturnValue) { | |
| if ($stack->isEmpty()) {// 堆栈已空 | |
| return; | |
| } | |
| // 找到之前的 gen | |
| $gen = $stack->pop(); | |
| // 把值发送到上个gen函数的yield表达式上 | |
| $gen->send($isReturnValue ? $value->getValue() : NULL); | |
| continue; | |
| } | |
| // 当前的gen还没有执行完毕 | |
| try { | |
| // yield 一对 key value | |
| // https://www.php.net/manual/en/class.generator.php | |
| $sendValue = (yield $gen->key() => $value); | |
| } catch (\Exception $e) { | |
| $gen->throw($e); | |
| continue; | |
| } | |
| // 发送收敛后的值 | |
| $gen->send($sendValue); | |
| } catch (\Exception $e) { | |
| if ($stack->isEmpty()) { | |
| throw $e; | |
| } | |
| $gen = $stack->pop(); | |
| $exception = $e; | |
| } | |
| } | |
| } | |
| // 函数参数嵌套yield | |
| function add($a, $b) { | |
| echo "a:$a b:$b\n"; | |
| return $a + $b; | |
| } | |
| function yield_value() { | |
| return 10; | |
| } | |
| function testFunc() { | |
| $res = yield add(yield yield_value(), 20); | |
| } | |
| $t = stackedCoroutine(testFunc()); | |
| echo "第一次：" . $t->current() . "\n"; | |
| $t->send($t->current()); | |
| echo "第二次：" . $t->current() . "\n"; | |
| $t->send(); | |
| if (!$t->valid()) { | |
| echo "generator is closed\n"; | |
| } | |
| ?> |
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