There's a fairly good implementation of co-routines called greenlets for python. It depends on a few basic API calls, these are:
1. g = greenlet.greenlet(fun) // makes a new greenlet pointing to the given function 2. g.switch(args) // switches to that function 3. g.switch(value) // once started delivers value inside that functions switch call 4. g.throw(error) // raises an exception into the function 5. greenlet.getcurrent() // returns the currently running greenlet With these API primitives, you can implement any flavor of asynchronous/concurrent scheduler on top if you wish to do so. On Wed, Nov 2, 2016 at 4:25 PM, Florian Bösch <[email protected]> wrote: > On Wed, Nov 2, 2016 at 4:13 PM, Bradley Meck <[email protected]> > wrote: > >> Florian, one of the great aspects of generators and async functions in >> ECMAScript is that they are explicit. It makes understanding where >> synchronization might need to occur very easy to find. I am unsure what >> your proposal to prevent infection as you call it would look like if it is >> explicit. >> > > The theory that await/async are explicit is nice, but flawed, and here's > why. > > If you have a call stack of say A -> B -> C -> D, and you change D to > async D, you have a problem. C isn't awaiting D, so it needs to do C await > -> async D, but now C isn't async and B isn't awaiting C, and so forth. So > you'll end up with an "infection": A await -> async B await -> async C > await -> async D. > > The infection spreads from down the call-stack upwards, and in doing so, > it spreads sideways as well. If you have say a routine that calls a bunch > of functions in succession: > > A(); B(); C(); D(); and for some reason or other (because your lower level > framework code became async) all of them now become awaitable as well, you > end up with await A(); await B(); await C(); await D(); > > So eventually most calls end up being prefixed by await and most > functions/methods end up being async, except for low-level code deep down. > > It might surprise you that co-routine schedulers work exactly like that. > Except without all the not needed line-noise. In fact, it could be argued > that instead of liberally strewing await/async randomly through your code, > you could simply do a preprocessor that converts every call to an await and > every closure to an async, that way at least you don't need to type it out > everytime. Of course you'd also get functionally true co-routines via a > fairly mindless application of preprocessing. >
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