DMD 0.148 - scope guard

[Regan Heath]

On Mon, 27 Feb 2006 21:05:33 -0800, S. Chancellor  
<dnewsgr at mephit.kicks-ass.org> wrote:
> On 2006-02-25 18:06:36 -0800, "Walter Bright"  
> <newshound at digitalmars.com> said:
>
>> Scope guards are a novel feature no other language has. They're based  
>> on Andrei Alexandrescu's scope guard macros, which have led to  
>> considerable interest in the idea. Check out the article  
>> www.digitalmars.com/d/exception-safe.html
>
> The only thing I see that's amazingly useful about this is the  
> on_scope_success.  Having a block of code that is only executed when an  
> exception is NOT thrown would be nice.  However, the rest of this stuff  
> seems like rocks under the water.  Your example of the new programmer  
> coming in reads like this to me:  "The new programmer may not take the  
> time to actually read the code he's modifying, so lets stick hidden  
> stuff in there to take care of things he might have missed."  Which  
> doesn't seem very logical to me, as it may be just as important to  
> modify those on success/on failure blocks and miss them.
>
> I'd say add another option to try..catch..finally paradigm.

You honestly don't think that this:

Transaction abc()
{
     Foo f;
     Bar b;
     Def d;

     f = dofoo();
     on_scope_failure dofoo_unwind(f);

     b = dobar();
     on_scope_failure dobar_unwind(b);

     d = dodef();

     return Transaction(f, b, d);
}

is better than this:

Transaction abc()
{
   Foo f;
   Bar b;
   Def d;

   f = dofoo();
   try {
     b = dobar();
     try {
       d = dodef();
       return Transaction(f, b, d);
     }
     catch(Object o) {
       dobar_unwind(b);
       throw o;
     }
   }
   catch(Object o) {
     dofoo_unwind(f);
     throw o;
   }
}

Regan