Avoiding Range Postblits

[Ali Çehreli via Digitalmars-d-learn]

On 02/18/2015 02:51 PM, "Nordlöw" wrote:

 > I'm guessing that move construction plays a key role here.

move() does avoid the post-blit but you get many destructions in return:

import std.stdio;
import std.algorithm;
import core.memory;

struct Graph
{}

struct DW
{
     int i;

     this(int i)
     {
         writefln(" this() for %s", i);
         this.i = i;
     }

     ~this()
     {
         writefln("~this() for %s", i);
     }

     this(this)
     {
         writefln("this(this) for %s", i);
         assert(false, "Oops");
     }
}

DW dw(Graph gr, int i)
{
     return DW(i);
}

void main()
{
     auto gr = Graph();
     auto arr = [ 1, 2, 3 ];
     auto dws = new DW[arr.length];

     foreach (i, el; arr) {
         auto source = gr.dw(el);
         move(source, dws[i]);
     }

     writeln(dws);
}

The output:

  this() for 1
~this() for 0
~this() for 0
  this() for 2
~this() for 0
~this() for 0
  this() for 3
~this() for 0
~this() for 0
[DW(1), DW(2), DW(3)]
~this() for 3
~this() for 2
~this() for 1

Ali