std.string.chomp error

[Lars T. Kyllingstad]

On Mon, 09 Aug 2010 17:35:56 -0700, Jonathan M Davis wrote:

> On Monday, August 09, 2010 17:09:03 simendsjo wrote:
>> On 10.08.2010 02:09, Jonathan M Davis wrote:
>> > On Monday, August 09, 2010 16:59:07 bearophile wrote:
>> >> simendsjo:
>> >>> Ahem.. :) Yes, I did miss your answer! How I got fooled by the
>> >>> preview pane and never noticed the scrollbar.
>> >> 
>> >> No problem, it happens, don't worry.
>> >> 
>> >>> I cannot see how your other bug report relates to this though.
>> >> 
>> >> My other bug report is about this line in your code:
>> >>   if (delimiter == null)
>> >> 
>> >> I don't like it :-)
>> >> 
>> >> Bye,
>> >> bearophile
>> > 
>> > Why, because it should be
>> > 
>> > if(delimiter is null)
>> > 
>> > 
>> > or just
>> > 
>> > if(!delimiter)
>> > 
>> > 
>> > - Jonathan M Davis
>> 
>> Hehe.. You're a bit beyond my D level right now. At least I now know
>> null == false and you can do reference is null :)
> 
> IIRC, you're not really supposed to do "delim == null" but rather us
> "delim is null" or shorten to to just "!delim". Why, I don't recall off
> the top of my head, but it might be because "delim == null" would be
> calling Object.opEquals(), and there's no need for that function call
> (though fortunately "delim == null" translates to Object.opEquals(delim,
> null) rather than delim.opEquals(null) which avoids issues where the lhs
> is null and causes it to go boom).
> 
> In either case, for null checks, I'd suggest either just using the
> reference by itself or to explictly use "is null" if you want the extra
> clarity.

No, using 'is' won't work.  Check this out:

  int[] a;
  assert (a == null);
  assert (a is null);

  a = new int[10];
  a.length = 0;
  assert (a == null);
  assert (a !is null);

The thing is, '==' tests whether two arrays are equal, that is, that they 
are equally long and that their elements are equal.  Any empty array is 
equal to null -- in fact, in this context 'null' is just a way of 
denoting an empty array that doesn't point to any particular memory block 
(i.e. hasn't been initialised yet).

  // This is what '==' does
  bool mimicEquals(int[] a, int[] b)
  {
      if (a.length != b.length) return false;
      foreach (i; 0 .. a.length) if (a[i] != b[i]) return false;
      return true;
  }

'is', on the other hand, tests whether two arrays are identical, i.e. 
that they have the same length and *refer to the same piece of memory*.

  // This is (sort of) what 'is' does
  bool mimicIs(int[] a, int[] b)
  {
     return (a.ptr == b.ptr  &&  a.length == b.length);
  }

-Lars