On Wednesday, 19 November 2014 at 16:02:50 UTC, David Gileadi
wrote:
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 <[email protected]> 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.
I'd say length being unsigned is fine. The real mistake is that
the difference between two unsigned values isn't signed, which
would be the most "correct" behaviour. Let people cast the result
if they want wrapping (or better, use a helper function to
document the intentiion).
