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D - foreach using namespaces

reply "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.
Dec 02 2003
parent 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
Dec 04 2003