on structs by reference

[Ali Çehreli via Digitalmars-d-learn]

On 11/14/2015 07:53 AM, Alex wrote:

 > 3. The only point I stumble on is, that the main feature in my program
 > is, that the underlying array, to which my slices refer to never
 > changes. So, I'm going to have more and more slices, which are going to
 > be smaller and smaller and each points to the same underlying array
 > without overlapping, but at each step, there are as much copies of a
 > single slice as elements it points to. I hope this last point was not
 > too weird.

Your struct objects must keep a reference to the slice that they use 
(i.e. one ore level of indirection).

Here is a start:

import std.stdio;

/* This is the storage to the slices that objects will share.
  *
  * (Surprisingly, creating a slice dynamically is not possible due
  * to syntax issues: new int[N] means "allocates N ints and make
  * a slice from those." However, we need a dynamic slice object
  * here. I've decided to put the slices in a 'slice slice' here.)
  */
int[][] slices;

struct S
{
     size_t idx;

     ref int[] arr()
     {
         return slices[idx];
     }
}

void main()
{
     S s; // = new S();
     slices ~= [1,2,3];
     s.idx = slices.length - 1;
     writeln(s.arr); //first

     S t; // = new S();
     t = s;
     writeln(t.arr); //second

     s.arr ~= 4;
     writeln(s.arr); //third
     writeln(t.arr);
}

[1, 2, 3]
[1, 2, 3]
[1, 2, 3, 4]
[1, 2, 3, 4]

Ali