Michel Fortin:
> But if one of your function has an 'out' parameter, it's impossible to
> implement the strong guarantee, as illustrated by this trivial example:
>
> void testOut(out int a) {
> throw new Exception("hello!");
> }
>
> void main() {
> int a = 2;
> try
> testOut(a);
> finally
> writeln(a);
> }
>
> Prints:
>
> 0
> object.Exception: hello!
>
> This happens because the out parameter gets reset to its default value
> as soon as you enter the function, so you can't throw an exception
> before it has been changed.
>
> So should 'out' be reformed to behave more like a return value? I'm not
> sure. But I think this is something to keep in mind when using out
> parameters.
In a recent post here:
http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D&article_id=110908
and in some successive answers I have tried to explain that out arguments are a
hack, they aren't as logically clean as multiple return values. I didn't think
about exceptions too, your example adds one more case to what I was saying
there. Thank you.
Bye,
bearophile
