• John C (20/20) Jul 17 2009 Is nesting foreach statements supposed to work? I hit a problem today th...
• Ary Borenszweig (35/64) Jul 17 2009 I can confirm that it's a bug. And I can see in Descent the testForeach
• Nick Sabalausky (8/31) Jul 17 2009 I came across a problem much like that a while back. Does this describe ...
• John C (3/12) Jul 17 2009 Looks like it's related, yes. I see that someone else has already noted ...

John C <johnch_atms hotmail.com> writes:

Is nesting foreach statements supposed to work? I hit a problem today that I've
never encountered before, even though I'm sure I've nested foreach before.
Here's an example that illustrates the problem:


class Collection {

  int opApply(int delegate(ref Object) a) {
    return 0;
  }

}

Object testForeach(Collection level1, Collection level2) {
  foreach (first; level1) {
    foreach (second; level2) {
      return second;
    }
  }
  return null;
}

void main() {
  testForeach(new Collection, new Collection);
}

Error: cannot implicitly convert expression (second) of type object.Object to
int

If someone else can repro this, I'll enter it into Bugzilla.

John.

Ary Borenszweig <ary esperanto.org.ar> writes:

John C escribió:
 Is nesting foreach statements supposed to work? I hit a problem today that
I've never encountered before, even though I'm sure I've nested foreach before.
Here's an example that illustrates the problem:
 
 
 class Collection {
 
   int opApply(int delegate(ref Object) a) {
     return 0;
   }
 
 }
 
 Object testForeach(Collection level1, Collection level2) {
   foreach (first; level1) {
     foreach (second; level2) {
       return second;
     }
   }
   return null;
 }
 
 void main() {
   testForeach(new Collection, new Collection);
 }
 
 Error: cannot implicitly convert expression (second) of type object.Object to
int
 
 If someone else can repro this, I'll enter it into Bugzilla.
 
 John.

I can confirm that it's a bug. And I can see in Descent the testForeach 
function is translated to this:

Object testForeach(Collection level1, Collection level2) {
   switch(level1.opApply(delegate (Object __applyArg0) {
     {
       Object first = __applyArg0;
       switch(level2.opApply(delegate (Object __applyArg0) {
         {
           Object second = __applyArg0;
           {
             // ** Here's the problem **
             __result = cast(Object) cast(int) second;
             return 2;
           }
         }
         return 0;
       } )) {
         default:
         break;
         case 2:
           __result = __result;
           return 2;
       }
     }
     return 0;
   } )) {
     default:
     break;
     case 2:
       return __result;
   }
   return cast(Object) null;
}

Maybe that helps fixing it. :-)

"Nick Sabalausky" <a a.a> writes:

"John C" <johnch_atms hotmail.com> wrote in message 
news:h3poo6$13j4$1 digitalmars.com...
 Is nesting foreach statements supposed to work? I hit a problem today that 
 I've never encountered before, even though I'm sure I've nested foreach 
 before. Here's an example that illustrates the problem:


 class Collection {

  int opApply(int delegate(ref Object) a) {
    return 0;
  }

 }

 Object testForeach(Collection level1, Collection level2) {
  foreach (first; level1) {
    foreach (second; level2) {
      return second;
    }
  }
  return null;
 }

 void main() {
  testForeach(new Collection, new Collection);
 }

 Error: cannot implicitly convert expression (second) of type object.Object 
 to int

 If someone else can repro this, I'll enter it into Bugzilla.

 John.

I came across a problem much like that a while back. Does this describe your 
problem?:
http://d.puremagic.com/issues/show_bug.cgi?id=2192

It looks like you're using iterable objects instead of AAs though. If you 
think it seems like basically the same bug, maybe update the ticket to 
indicate the problem is more general than just AAs. 

John C <johnch_atms hotmail.com> writes:

Nick Sabalausky Wrote:

 I came across a problem much like that a while back. Does this describe your 
 problem?:
 http://d.puremagic.com/issues/show_bug.cgi?id=2192
 
 It looks like you're using iterable objects instead of AAs though. If you 
 think it seems like basically the same bug, maybe update the ticket to 
 indicate the problem is more general than just AAs. 
 
 

Looks like it's related, yes. I see that someone else has already noted that
the problem happens with opApply, too.

Cheers.