Signed-unsigned comparisons in Phobos

[Simen Kjaeraas]

On Fri, 12 Aug 2011 14:55:26 +0200, Marco Leise <Marco.Leise at gmx.de> wrote:

> Am 12.08.2011, 12:22 Uhr, schrieb kennytm <kennytm at gmail.com>:
>
>> Don <nospam at nospam.com> wrote:
>>
>>> I've had a look at a dozen or so of these, and they were all real. I
>>> didn't see any which require a cast to "make the compiler shut up".
>>> That's pretty impressive. In C++ I find that such messages are nearly
>>> always false positives.
>>>
>>> The one case where it's a bit annoying is this:
>>>
>>> int [] x = new int[6]; // or x = some array literal.
>>> for (int i = 0; i < x.length; ++i) {...}
>>>
>>> Here is a suggestion for how we could eliminate such false positives.
>>> http://d.puremagic.com/issues/show_bug.cgi?id=6478
>>
>> Doesn't this require flow analysis? And the type of index 'i' should be
>> 'size_t' anyway.
>
> I think I once shot myself in the foot with this when I used 'auto' for  
> 'i' and the code wouldn't compile on x86_64, because I assigned the  
> variable to an int or uint later on in the loop. You just have to be  
> aware that this is an unsigned integer of machine word length. So I  
> agree with kennytm on this.
>
> Just remember that reverse loops are written like this:
>
> for (size_t i = x.length; i-- > 0; ) {...}

I like using the long arrow operator for this:
   i --> 0 // i goes to 0

-- 
   Simen