Signed word lengths and indexes

[BCS]

Hello Steven,

> On Mon, 14 Jun 2010 21:48:10 -0400, BCS <none at anon.com> wrote:
> 
>> Hello Steven,
>> 
>>> div0 <div0 at users.sourceforge.net> writes:
>>> 
>>>> for(uint i = end - 1; i < length; --i)
>>>> ...
>>> What does "length" represent here? It's not clear to me how "i"
>>> descending toward zero is going to break the guard condition.
>>> 
>> My thought exactly.
>> 
>> If i<j and you --i, I'd assume i<j, if your code depends on the case
>> where the assumption is wrong, don't ask me to do a code review
>> because  I won't sign off on it.
>> 
> i is unsigned, and therefore can never be less than 0.  It's actually
> a  clever way to do it that I've never thought of.

It's /to/ clever. That's the problem. If you haven't seen it in a while, 
it's confusing and it LOOKS wrong even if you have.

> 
> Read it more like this:
> 
> for(uint i = end - 1; i < length && i >= 0; --i)
> 
> But the i >= 0 is implicit because i is unsigned.
> 

I know, that's exactly "the case where the assumption is wrong".

-- 
... <IXOYE><