'int' is enough for 'length' to migrate code from x86 to x64

[David Gileadi via Digitalmars-d]

On 11/19/14, 6:57 AM, ketmar via Digitalmars-d wrote:
> On Wed, 19 Nov 2014 13:47:50 +0000
> Don via Digitalmars-d <digitalmars-d at puremagic.com> wrote:
>> If I have two pencils of length 10 cm and 15 cm, then the first
>> one is -5 cm longer than the other.
> and again "length" is not a relation. show me pencil of length -10 cm.
> when you substractin lengthes, you got completely different type as a
> result, not "length" anymore. ah, that untyped real-life math! ;-)

To me the salient point is that this is not just a mess with real-life 
math but also with math in D: lengths are unsigned but people subtract 
them all the time. If they're (un)lucky this will return correct values 
for a while, but then someday the lengths may be reversed and the values 
will be hugely wrong:

     int[] a = [1, 2, 3];
     int[] b = [5, 4, 3, 2, 1];

     writefln("%s", b.length - a.length);  // Yup, 2
     writefln("%s", a.length - b.length);  // WAT? 18446744073709551614

This is why I agree with Don that:

 > Having arr.length return an unsigned type, is a dreadful language
 > mistake.