Re: [Vala] Implicit lamdas/closures

["Christian Hergert" <christian hergert gmail com>]

This sounds particularly interesting to implement.  As we would almost certainly need some sort of "Async Handle" to work with.  .NET has IAsyncResult, Twisted has Deferred, etc.  What makes this tough is that it would require some sort of addition to GLib unless we were to require an extra library like Gee.  However, I guess we could generate a special struct that is used for this handle.

Of course, I could be totally wrong here and someone may have a clever way around this.  I'll let it stew in my head over night; anyone else have thoughts on this?

-- Christian

On Tue, Sep 16, 2008 at 4:28 PM, Samuel Cormier-Iijima <sciyoshi gmail com> wrote:

On Tue, Sep 16, 2008 at 6:43 PM, Jürg Billeter <j bitron ch> wrote:
> On Tue, 2008-09-16 at 15:39 -0700, Christian Hergert wrote:
>> I absolutely love the yield idea, very python-twisted'ish.  Lets make
>> sure the yield can return a value as well so we can have the
>> following:
>>
>> var value = yield obj.do_something ();
>
> Sure, return values should certainly be possible.

I'd love to see this in Vala - it would make asynchronous programming
much nicer. Would there be a syntax for specifying what types can be
sent in to the iterator/coroutine (assuming that the yield syntax
could be used for general iterators), or would yield always have to be
used with the _async/_finish API (and value's type inferred from the
sync version of the call)? Also, what would the C API look like for
these - functions that return GClosures or automatically-generated
sync/async versions of the function? I'm guessing that Vala could
automatically determine which one to do if it sees that you're
returning the result of a method marked as async-able, or maybe there
should be different keywords for either case... For example:

string do_something(Socket sock) {
   try {
       yield sock.connect();
   } catch (Error e) {
       return null;
   }

   var data = "" socket.read(5);

   return data;
}

Might be nice if this generated do_something, do_something_async, and
do_something_finish automatically.

--
Samuel Cormier-Iijima <sciyoshi gmail com>