On the richness of C++

[Bruno Medeiros]

Jason House wrote:
> 
> 
>>> Closures capture variables by reference.  This means that creating
>>> delegates inside a foreach loop (with deferred evaluation) could fail
>>> to have the expected behavior.  Bind stores stuff by value, so I
>>> still find myself using bind libraries.
>> If you expect captured variables to be by value, sure. But I always
>> expected them to be by reference!
> 
> By reference is nice in many cases, but in others it's frustrating.  How do
> you implement the following?
> 
> foreach(job; queue)
>   runthread(void delegate(){job.execute;});
> 
> (Somehow I expect someone to pick apart the example, but I hope the point is
> clear)


This way:

   foreach(job; queue) {
     ({
       auto myjob = job;
       runthread(void delegate(){myjob.execute;});
     })();
   }

And I'm pretty sure that it is only due to a bug that this doesn't work:

   foreach(job; queue) {
     auto myjob = job;
     runthread(void delegate(){myjob.execute;});
   }

(I'll file a report)

Like Walter said, it's a lot harder to make by-value closures into 
by-reference than the other way around. You may bask in the glory of D 
now. :)


-- 
Bruno Medeiros - Software Developer, MSc. in CS/E graduate
http://www.prowiki.org/wiki4d/wiki.cgi?BrunoMedeiros#D