please help me to reverse a function call order

[rikki cattermole]

A bit more d-ified and uses foreach + foreach_reverse without allocating 
an array.

```d
import std.stdio;

void main()
{
     doRepetition(4, 3);
     writeln("==========");
     doRepetitionReversed(4, 3);
}

void doRepetition(const int n, const int m)
{
     // combination total number is m,  element is repeatable.
     assert(n >= 1 && n < 10);
     assert(m >= 1 && m < 10);
     enum N = 10;
     ubyte[10] a;
     void inc(int index, int r, int start, int end)
     {
         if (index == r)
         {
             // get one unique combination result, not repeatable
             foreach (j; 0 .. r)
             {
                 writef!"%d "(a[j]);
             }
             writeln;
             return;
         }

         foreach (i; start .. end)
         {
             a[index] = cast(ubyte) i;
             inc(index + 1, r, i, end);
         }
     }

     inc(0, m, 0, n);
}

void doRepetitionReversed(const int n, const int m)
{
     // combination total number is m,  element is repeatable.
     assert(n >= 1 && n < 10);
     assert(m >= 1 && m < 10);
     enum N = 10;
     ubyte[10] a;
     void inc(int index, int r, int start, int end)
     {
         if (index == r)
         {
             // get one unique combination result, not repeatable
             foreach_reverse (j; 0 .. r)
             {
                 writef!"%d "(a[j]);
             }
             writeln;
             return;
         }

         foreach_reverse (i; start .. end)
         {
             a[index] = cast(ubyte) i;
             inc(index + 1, r, i, end);
         }
     }

     inc(0, m, 0, n);
}
```

Output:

```
0 0 0
0 0 1
0 0 2
0 0 3
0 1 1
0 1 2
0 1 3
0 2 2
0 2 3
0 3 3
1 1 1
1 1 2
1 1 3
1 2 2
1 2 3
1 3 3
2 2 2
2 2 3
2 3 3
3 3 3
==========
3 3 3
3 3 2
3 2 2
2 2 2
3 3 1
3 2 1
2 2 1
3 1 1
2 1 1
1 1 1
3 3 0
3 2 0
2 2 0
3 1 0
2 1 0
1 1 0
3 0 0
2 0 0
1 0 0
0 0 0
```