coroutine | 易学教程

Scanner and parser interaction

阅读更多关于 Scanner and parser interaction

问题 I am new to flex/bison. Reading books, it seems that in nearly all compiler implementations, the parser interacts with the scanner in a "coroutine" manner, that whenever the parser needs a token, it calls the scanner to get one, and left the scanner aside when it's busy on shift/reduce. A natural question is that why not let the scanner produces the token-stream (from the input byte-stream) as a whole, and then pass the entire token-stream to the parser, thus there is no explicit interaction

How to unit test coroutine when it contains coroutine delay?

阅读更多关于 How to unit test coroutine when it contains coroutine delay?

问题 When I add a coroutine delay() in my view model, the remaining part of the code will not be executed. This is my demo code: class SimpleViewModel : ViewModel(), CoroutineScope { override val coroutineContext: CoroutineContext get() = Dispatchers.Unconfined var data = 0 fun doSomething() { launch { delay(1000) data = 1 } } } class ScopedViewModelTest { @Test fun coroutineDelay() { // Arrange val viewModel = SimpleViewModel() // ActTes viewModel.doSomething() // Assert Assert.assertEquals(1,

Python: I don't understand what's happening with this generator

阅读更多关于 Python: I don't understand what's happening with this generator

问题 I'm curious as to what's happening here. Can someone who knows generators and coroutines well explain this code. def b(): for i in range(5): yield i x = (yield) print(x) def a(): g = b() next(g) for i in range(4): g.send(5) print(next(g)) a() output None 1 None 2 None 3 None 4 but when I switch around lines 3 and 4: the lines yield i and x = (yield) , I get the following. 5 None 5 None 5 None 5 None I suspect the problem might me from trying to use the yield statement to both receive and send

How to run suspend method via reflection?

阅读更多关于 How to run suspend method via reflection?

问题 There is an coroutine block that can runs suspend functions. But I call the function by invoke via reflection. This is java style invocation, apparently a simple call will not work. Are there ways to run reflected method asynchronously? How to await this method? import kotlin.coroutines.experimental.* class TestClass(val InString: String) { suspend fun printString() { println(InString) } } fun launch(context: CoroutineContext, block: suspend () -> Unit) = block.startCoroutine

How await keyword works?

阅读更多关于 How await keyword works?

问题 For a given below co-routine( f ), import csv import urllib def f(resp): print('Line 1') yield csv.reader(resp.read().decode('utf-8')) def h(): url = 'http://www.nasdaq.com/screening/companies-by-industry.aspx?exchange=NYSE&render=download' resp = urllib.urlopen(url) cr = f(resp) cr = f(resp) assigns an iterator object to cr , cr.next() execute Line 1 and block at yield keyword. My understanding is, with syntax cr=f(resp) there is no event-loop(task scheduler) with threading, behind the scene

How can I use coroutines with volley so that my code can be written like sychronous?

阅读更多关于 How can I use coroutines with volley so that my code can be written like sychronous?

问题 Here's an example from developer.android.com class MainActivity : AppCompatActivity() { lateinit var textView:TextView lateinit var button:Button override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) textView = findViewById(R.id.textView) button = findViewById(R.id.button) button.setOnClickListener({ getData() }) } fun getData(){ val queue = Volley.newRequestQueue(this) val url = "http://www.google.com/" val

libcoro:在c++中支持coroutine

阅读更多关于 libcoro:在c++中支持coroutine

起因在第一个版本的 libtnet 开发完成之后，我一直在思考如何让异步方式的网络编程更加简单。虽然 libtnet 通过c++ shared_ptr以及function等技术很大程度上面解决了异步代码编写的一些问题，但是仍然会出现代码逻辑被强制拆分的情况。而这个则是项目中童鞋无法很好的使用其进行开发的原因。所以我考虑让 libtnet 支持coroutine。 Coroutine 第一次接触coroutine的概念是在lua里面，记得当时想了很久才算弄明白了coroutine的使用以及原理。在lua中，coroutine的使用如下： co = coroutine.create(function () print("begin yield") coroutine.yield() print("after yield") end) coroutine.resume(co) print("after resume") coroutine.resume(co) 我们可以通过resume执行一个新创建或者已经被挂起的coroutine，通过yield挂起当前的coroutine，这样就可以实现类似多线程方式下面的多任务调度。至于coroutine的原理，很多地方都有说明，主要就在于每个coroutine都有自己的堆栈，这样当coroutine挂起的时候，它的当前执行状态会被完整保留

How to implement coroutine within for loop in c

阅读更多关于 How to implement coroutine within for loop in c

问题 Here is part code: void a() { printf("entering a\n"); int i; for(i = 0; i < 3; i++){ if(setjmp(a_buf) == 0) { printf("A step %d\n", i); b(); } else { longjmp(b_buf, 1); } } printf("returning from a\n"); } void b() { printf("entering b\n"); int i; for(i = 0; i < 5; i++){ if(setjmp(b_buf) == 0) { printf("B step %d\n", i); a(); } else { longjmp(a_buf, 1); } } printf("returning from b\n"); } I have two processes a & b . How to make them works as coroutine. Wish them doing A Step 0 then B Step 0

Will a Python generator be garbage collected if it will not be used any more but hasn't reached StopIteration yet?

阅读更多关于 Will a Python generator be garbage collected if it will not be used any more but hasn't reached StopIteration yet?

问题 When a generator is not used any more, it should be garbage collected, right? I tried the following code but I am not sure which part I was wrong. import weakref import gc def countdown(n): while n: yield n n-=1 cd = countdown(10) cdw = weakref.ref(cd)() print cd.next() gc.collect() print cd.next() gc.collect() print cdw.next() On the second last line, I called garbage collector and since there is no call to cd any more. gc should free cd right. But when I call cdw.next() , it is still

Wait for the termination of n goroutines

阅读更多关于 Wait for the termination of n goroutines

问题 I need to start a huge amount of goroutines and wait for their termination. The intuitive way seems to use a channel to wait till all of them are finished : package main type Object struct { //data } func (obj *Object) Update(channel chan int) { //update data channel <- 1 return } func main() { channel := make(chan int, n) list := make([]Object, n, m) for { for _, object := range list { go object.Update(channel) } for i := 0; i < n; i++ { <-channel } //now everything has been updated. start