const?? When and why? This is ugly!

[Derek Parnell]

On Sat, 07 Mar 2009 23:40:52 -0800, Walter Bright wrote:

> I'm still not understanding you, because this is a contrived example 
> that I cannot see the point of nor can I see where it would be 
> legitimately used.

I can see Burton's concern, and I'm very surprised that the compiler allows
this to happen. Here is a slightly more explicit version of Burton's code.

import std.stdio;
void main()
{
  int [] a = new int [1];

   a [0] = 1;

   invariant (int) [] b = cast (invariant (int) []) a;

   writef ("a=%s b=%s\n", a [0], b[0]);
   a [0] += b [0];
   writef ("a=%s b=%s\n", a [0], b[0]);
   a [0] += b [0];
   writef ("a=%s b=%s\n", a [0], b[0]);
}
   
The problem is that we have declared 'b' as invariant, but the program is
allowed to change it. That is the issue.

-- 
Derek Parnell
Melbourne, Australia
skype: derek.j.parnell