On 11/19/14 10:09 AM, Ary Borenszweig wrote:
On 11/19/14, 7:03 AM, Don wrote:
On Tuesday, 18 November 2014 at 18:23:52 UTC, Marco Leise wrote:
>
Weird consequence: using subtraction with an unsigned type is nearly
always a bug.
I wish D hadn't called unsigned integers 'uint'. They should have been
called '__uint' or something. They should look ugly. You need a very,
very good reason to use an unsigned type.
We have a builtin type that is deadly but seductive.
I agree. An array's length makes sense as an unsigned ("an array can't
have a negative length, right?") but it leads to the bugs you say. For
example:
~~~
import std.stdio;
void main() {
auto a = [1, 2, 3];
auto b = [1, 2, 3, 4];
if (a.length - b.length > 0) {
writeln("Can you spot the bug that easily?");
}
}
~~~
Yes, it makes sense, but at the same time it leads to super unintuitive
math operations being involved.
Rust made the same mistake and now a couple of times I've seen bugs like
these being reported. Never seen them in Java or .Net though. I wonder
why...
There are related bugs in Java too, e.g. I remember one in binary search
where (i + j) / 2 was wrong because of an overflow. Also, Java does have
a package for unsigned integers so apparently it's necessary.
Andrei
