Question

I am playing around with D arrays and I stumbled upon this:

When I compile this code

import std.stdio;

int main()
{
  int[] a, b;
  b ~= [2,3,4,5];
  a.length = b.length;
  a[] = b[] + 4;
  writeln(typeid(a),"\n",typeid(b));
  writeln(a,"\n",b);

  int[] c, d;  
  for (int n=10; n<20; ++n) {
    d ~= n;

  }
  c.length = d.length;
  c = d[] + 2;  //compile error
  writeln(typeid(c),"\n",typeid(d));
  writeln(c,"\n",d);

  return 0;
}

I get an error at compilation:

Error: Array operation d[] + 2 not implemented

Ht only difference between the first few lines and the rest is the way b and d are filled.

How can I use array operations with an array filled in a loop?

And another question:

Are the first few lines the right way to do it? The line a.length = b.length; seems a little odd to me.

Answer 1

First question: You just forgot [] on the left side. c[] = d[] + 2; works.

Second question: Yes; vector operations need arrays of equal size, and setting .length is one way to resize an array.