On May 13, 2013, at 4:15 PM, David Herman <dher...@mozilla.com> wrote:
> On May 13, 2013, at 11:07 AM, Allen Wirfs-Brock <al...@wirfs-brock.com> wrote:
>
>> It closes down this whole edge-case focused discussion and that's valuable
>> in itself. Also, since it turns try {yield expr} finally{} into a syntax
>> error we could revisit the decision in a future edition if somebody
>> actually comes up with compelling use cases.
>
> I'm very uncomfortable with this restriction. Ad hoc restrictions break
> compositionality. They come back to bite you because you broke generality for
> want of use cases, when we all know we can't predict all the use cases of a
> general-purpose programming mechanism. This gets our responsibility
> backwards: ad hoc restrictions that break generality should be extremely
> strongly motivated, rather than requiring use cases for the semantics they
> disallow.
And what was I thinking, of course there are use cases: anything where you'd
use try/finally in a language with synchronous I/O, you would use try/finally
in task.js.
spawn(function*() {
let splashScreen = $("splash");
try {
splashScreen.style.display = 'block';
let assets = yield downloadAssets();
// ...
} catch (e) {
// ...
} finally {
splashScreen.style.display = 'none';
}
});
Dave
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