First Draft: Coroutines

[ryuukk_]

On Monday, 5 August 2024 at 01:36:31 UTC, Richard (Rikki) Andrew 
Cattermole wrote:
> Coroutines is a stack machine transformed representation for a 
> function. It enables storing the state of a function externally 
> to the stack to allow for high throughput event handling.
>
> Latest: 
> https://gist.github.com/rikkimax/fe2578e1dfbf66346201fd191db4bdd4
>
> Current: 
> https://gist.github.com/rikkimax/fe2578e1dfbf66346201fd191db4bdd4/0bb4442c092e061d520c35a43278f0819666f26f
>
> It uses the ``@async`` attribute to transform into a type that 
> is used to describe the function, with the help of implicit 
> conversions using knowable library types and a hook for 
> construction to produce a library object that represents the 
> function.
>
> There is support for such UDA's as ``@Route`` to make the 
> function automatically marked as ``@async`` to prevent explicit 
> annotation requirement.
>
> An example usage of one:
>
> ```d
> void clientCO(Socket socket) @async {
> 	writeln("Connection has been made");
>
> 	socket.write("GET / HTTP/1.1\r\n");
> 	socket.write("Accept-Encoding: identity\r\n");
> 	socket.write("\r\n");
>
> 	while(Future!string readLine = socket.readUntil("\n")) {
> 		if (!readLine.isComplete) {
> 			writeln("Not alive and did not get a result");
> 			return;
> 		}
> 		
> 		string result = readLine.result;
> 		writeln(result);
>
> 		if (result == "</html>") {
> 			writeln("Saw end of expected input");
> 			return;
> 		}
> 	}
> }
> ```

C#'s async model is not an example to follow, your `Future!T` is 
the proof

There should be no distinction between an async/sync function