• Salih Dincer (55/55) Sep 27 😁

Salih Dincer <salihdb hotmail.com> writes:

😁

Try the 2nd usage, D is a very flexible language; moves towards 
perfection!

```d
struct Sarma {
     int i;
     // mixin DownRange;
}

struct Foo(T) {
     int[] array;
                        // 1. USAGE
     auto opApply(scope int delegate(T) dg) {
         foreach (ref e; array)
         {
             auto result = dg(T(e));
         }
         return 0;
     }

     auto opApply(scope // 2. USAGE
     int delegate(size_t, int, ref int) dg) {
         int count;
         foreach (i, ref e; array)
         {
             e *= 15;
             ++count;
             auto result = dg(i, count, e);
         }
         return 0;
     }
}
import std.stdio;
void main()
{
     auto foo = Foo!Sarma( [2, 4, 6] );

     foreach (Sarma e; foo)
     {
         e.write(" ");
     }
     writeln;

     foreach (i, s, ref e; foo)
     {
         s.writef!"counter = %s, ";
         i.writeln(": ", e++);
     }
     foo.array.writeln;
}

template DownRange() {
     bool empty() { return i <= 0; }
     auto front() { return i; }
     void popFront() { --i; }
}
```

It may be explained in specific documentation (on 12.11.11).

https://dlang.org/spec/statement.html#foreach_over_arrays

SDB 79