Yeah, I was mostly responding to your earlier comment that casting
didn't work for you. If you really wanted to cast it would be to
ptrdiff_t anyway.
I agree that there's a more fundamental problem though. Weren't we
going to make implicit narrowing conversions an error? I know it
isn't in the spirit of c, but c allows all sorts of horrible nonsense.
Sent from my iPhone
On Jan 21, 2010, at 8:22 AM, Andrei Alexandrescu <[email protected]>
wrote:
On a 64-bit system you have a portability problem. Generally casts
are bad because they specify the target type when you actually want
a different manipulation (in this case, changing signedness).
std.traits has a function called "unsigned" that takes an integral
of any length and returns the corresponding unsigned integral. I'll
define also "signed". With that and with the change to abs(), abs(j
- i) is an error (static assert), and will actually suggest that you
use abs(signed(j - i)) in its error message.
At any rate, all these fixes don't make me feel much better. Bugs
are easy to come by and difficult to find (my initial code involved
an associative array, and AAs have their _own_ bugs that made me
suspicious).
In brief, D still has big problems with handling signed and unsigned
integrals.
Andrei
Sean Kelly wrote:
I got a reasonable answer by casting to int before calling abs():
import std.math, std.stdio;
void main() {
auto a = [ 4, 4, 2, 3, 2 ];
float avgdist = 0;
uint count;
foreach (i, e1; a) {
foreach (j, e2; a) {
if (i == j) continue;
if (e1 != e2) continue;
++count;
writeln("adding ", cast(int)(i - j));
avgdist += abs(cast(int)(i - j));
}
}
writeln(count, " ", avgdist / count);
}
On Jan 21, 2010, at 12:41 AM, Andrei Alexandrescu wrote:
The problem persists even if I remove the call to abs(). At least
its removal makes things look more suspicious.
Andrei
Don Clugston wrote:
2010/1/21 Sean Kelly <[email protected]>:
My first inclination would be for abs to only accept signed
values. Unsigned values don't really seem appropriate for
unchecked math operations.
I agree, it doesn't make sense to take the absolute value of
something
which doesn't have a sign. With range checking, it ought to be
possible to implicitly cast from uint to int, which would allow
all of
the sensible uses. Unfortunately, implicit casting and templates
don't
interact well. So I think abs() might need to go back to being a
non-template function.
On Jan 20, 2010, at 8:50 PM, Andrei Alexandrescu wrote:
Is there anything we can do about this?
Andrei
-------- Original Message --------
Subject: "Unsigned-related bugs never occur in real code."
Date: Wed, 20 Jan 2010 20:42:50 -0800
From: Andrei Alexandrescu <[email protected]>
Organization: Digital Mars
Newsgroups: digitalmars.D
"It's an academic problem. Don't worry about it and move on."
That's what Walter kept on telling me. Yet I've spent the
better part of
an hour reducing a bug down to the following:
import std.math, std.stdio;
void main() {
auto a = [ 4, 4, 2, 3, 2 ];
float avgdist = 0;
uint count;
foreach (i, e1; a) {
foreach (j, e2; a) {
if (i == j) continue;
if (e1 != e2) continue;
++count;
avgdist += abs(i - j);
}
}
writeln(count, " ", avgdist / count);
}
May this post be an innocent victim of the war against unsigned-
related
bugs.
Andrei
_______________________________________________
phobos mailing list
[email protected]
http://lists.puremagic.com/mailman/listinfo/phobos
_______________________________________________
phobos mailing list
[email protected]
http://lists.puremagic.com/mailman/listinfo/phobos
_______________________________________________
phobos mailing list
[email protected]
http://lists.puremagic.com/mailman/listinfo/phobos
_______________________________________________
phobos mailing list
[email protected]
http://lists.puremagic.com/mailman/listinfo/phobos
_______________________________________________
phobos mailing list
[email protected]
http://lists.puremagic.com/mailman/listinfo/phobos
_______________________________________________
phobos mailing list
[email protected]
http://lists.puremagic.com/mailman/listinfo/phobos
_______________________________________________
phobos mailing list
[email protected]
http://lists.puremagic.com/mailman/listinfo/phobos
