D - more or less power than C++?

[Sean Kelly]

Walter Bright wrote:
> "Andrew Fedoniouk" <news at terrainformatica.com> wrote in message 
> news:dubfs7$95p$1 at digitaldaemon.com...
>>
>> 1) Again, what will happen if on_scope_success will throw?
> 
> I believe I answered that. Throwing in on_scope is like throwing in a 
> destructor or in a finally block. It's a very bad idea, and will probably 
> produce a double fault exception. The same issue exists with C++.

DMD will throw the new exception and the old one will be discarded. 
.NET (or C# at any rate) has the same basic behavior, though it may be 
the the original exception that is retained in .NET, I can't remember 
offhand.  I think the current approach is arguably better than a call to 
terminate, as the C++ approach reduces the general utility of RAII.

>> 2) As I said before, implementation of on_scope_success
>> seems like artificial  to D. In syntax and in implementation.
> 
> If by that you mean it is unique to D, then yes, it is. But it is based on 
> work done by experts in the field who have attempted to bash C++ into doing 
> it, and those experts have reviewed on_scope. They've helped me understand 
> what the issues are, and what the solution should look like, and I've 
> implemented that solution. So I have a lot of confidence that it is the 
> right solution.
> 
> I know that it's unfamiliar, and it took me a while to get it. 

For what it's worth, Andrei has put all of his articles online at 
http://erdani.org/publications/  His original article on ScopeGuard is 
well worth reading.  A direct link is here: 
http://www.cuj.com/documents/s=8000/cujcexp1812alexandr/alexandr.htm


Sean