Re: [KJ] [RFC] Regarding abs() and labs()

[Richard Knutsson <ricknu-0@student.ltu.se>]

Randy Dunlap wrote:
> On Sat, 03 Feb 2007 03:22:29 +0100 Richard Knutsson wrote:
>
>   
>> Randy Dunlap wrote:
>>     
>>> On Sat, 03 Feb 2007 02:13:44 +0100 Richard Knutsson wrote:
>>>
>>>   
>>>       
>>>> Hello all
>>>>
>>>> Just took a look at abs() and can not understand why it seem so 
>>>> overcomplicated. Why not just:
>>>>
>>>> #define abs(x)	((x) < 0) ? -(x) : (x))
>>>>     
>>>>         
>>> It's almost that simple.  It just adds a local __x so that
>>> 'x' won't be evaluated multiple times as it would in the simpler
>>> version.  Multiple evaluations (of an expression) (that could
>>> have side effects) would take more CPU horsepower and could
>>> have bad side effects as well.
>>>   
>>>       
>> You mean if x is ex a + b? In such case; why not use typeof instead of int?
>>     
>
> I suppose that would make sense if we have a need for abs(various types),
> but until we do, just using: int __x; is good enough.
>   
Mm, true. Don't mess with something that is not broken (if not for the 
fun of it).
But that really leaves labs() hanging. I guess it was added because it 
is in gcc's stdlib.h.
>> What kind of side-effects are you talking about?
>>     
>
> The usual kind that affect computer software.  E.g.:
>
> 	a = abs(var1++);
>   
Oh thanks, good "eye-opener" :)

Thanks for clearing things up
Richard Knutsson

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