Signed word lengths and indexes

[BCS]

Hello Steven,

> On Tue, 15 Jun 2010 10:08:38 -0400, BCS <none at anon.com> wrote:
> 
>> 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.
>> 
> This is easily solved - put in a comment.  I frequently put comments
> in my  code because I know I'm going to forget why I did something.


All else being equal, code that *requiters* comments to understand is inferior 
to code that doesn't.

>>> 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".
>> 
> Reading code assuming integer wrapping never occurs is a big mistake.
> You  should learn to assume wrapping is always possible.
> 

You should learn to write code where I and everyone else doesn't /need/ to 
assume it is possible.

(personably, I find it marginally offensive/greedy when someone's first proposal 
as to how to fix a problem if for the rest of the world to change and the 
second option is for the person to change.)

-- 
... <IXOYE><