• "Vathix" <vathix dprogramming.com> Dec 02 2003
• J Anderson <REMOVEanderson badmama.com.au> Dec 04 2003

"Vathix" <vathix dprogramming.com> writes:

Using a namespace we could have separate foreach's:

class Foo
{
 int opApply(int delegate(inout int) dg);

 namespace reverse
 {
  int opApply(int delegate(inout int) dg);
 }
}

int main()
{
 Foo foo = new Foo;
 foreach(int i; foo) { }
 foreach(int i; foo.reverse) { }

 return 0;
}

That would obviously go over the elements in reverse order. There could also
be others: foreach depending on certain attributes such as for a file list,
a directory namespace with opApply that only goes over the directories.

J Anderson <REMOVEanderson badmama.com.au> writes:

Vathix wrote:

Using a namespace we could have separate foreach's:

class Foo
{
 int opApply(int delegate(inout int) dg);

 namespace reverse
 {
  int opApply(int delegate(inout int) dg);
 }
}

int main()
{
 Foo foo = new Foo;
 foreach(int i; foo) { }
 foreach(int i; foo.reverse) { }

 return 0;
}

That would obviously go over the elements in reverse order. There could also
be others: foreach depending on certain attributes such as for a file list,
a directory namespace with opApply that only goes over the directories.



  


Of course you can do this now:

class FooR
{
 this(Foo other) { Other = other; }
 int opApply(int delegate(inout int) dg) { return 0; }

 Foo Other;
}


class Foo
{
 int opApply(int delegate(inout int) dg) { return 0; }
 FooR reverse()   { return new FooR(this);  }
}


int main( char [] [] args )
{

    Foo foo = new Foo;
    foreach(int i; foo) { }
    foreach(int i; foo.reverse()) { }

   return 1;
}

But it's not quite as concise or efficient. If this syntax sugar was to 
be brought in, It wouldn't be limit it to opApply opperators. Parhaps 
it's a way to encourage opperator reuse in opperator overloading.

foo.w ~ foo2.w ~ foo3.w;
foo.r ~ foo2.r ~ foo3.r;

-Anderson