[MacRuby-devel] Return from thread context

[Charles Oliver Nutter]

On Fri, Jul 10, 2009 at 3:02 PM, Laurent
Sansonetti<lsansonetti at apple.com> wrote:
> Now, consider:
>
> def foo
>  begin
>    yield
>  ensure
>    p :ok
>  end
> end
> def bar
>  foo { return 42 }
> end
> p bar
>
> Here you don't have a choice, since you need to honor the ensure block.
>
> In Ruby, return is semantically similar to an exception in some cases. This
> is unfortunate :-)

Return isn't really an exception, since you can't catch/rescue it. The
issue here is that ensure blocks are a hard requirement, and they must
fire even if a non-local return unrolls through them. The return here
doesn't necessarily need to be implemented as an exception, but it
does need to fire ensure blocks.

In JRuby, we do use an exception, but we don't have any other way of
unrolling the stack.

- Charlie