Re: [boost] Re: Re: Constrained genericity at last? (any interestinanoperator traits/concept traits library?)

From: Victor A. Wagner Jr. (vawjr_at_[hidden])
Date: 2004-09-27 11:04:38

OOps
At Monday 2004-09-27 01:02, you wrote:
>At Sunday 2004-09-26 17:35, you wrote:
>> > Victor A. Wagner Jr. <vawjr_at_[hidden]> wrote:
>> > The midpoint between them is (this is legal using your constraints):
>> >
>> > a + (b-a)/2
>> >
>> > 1st year algebra teaches us that this is equivalent to:
>> >
>> > (a+b)/2
>> >
>> > While on most systems the intermediate value (a+b) would be useless, as
>> > soon as you divide by 2 it again becomes useful.
>> >
>> > with a third pointer (T* c;):
>> >
>> > (a+b+c)/3
>> >
>> > becomes calculable and useful though clearly
>>
>>Just a small $0.02...
>>
>>(a + b) is a dangerous thing in a 32 bit world full of arithmetic
>>overflow opportunities.  You'd have to have a very good reason for
>>doing it this way I'd think.
>>
>>a + (a-b) / 2 is a bit safer
>
>I don't see the safety issue and what you showed is incorrect; a + (b-a) / 
>2   is at least correct, but b-a overflows just as readily as a+b

I should know better than to try this stuff at 0100 local.  Of course (b-a) 
is less likely to overflow than (a+b).  It's certainly fair to presume that 
the _size_ of any such container will be small in comparison to the range 
addresses

>>matt
>>matthurd_at_[hidden]
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>Victor A. Wagner Jr.      http://rudbek.com
>The five most dangerous words in the English language:
>               "There oughta be a law"
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Victor A. Wagner Jr.      http://rudbek.com
The five most dangerous words in the English language:
               "There oughta be a law"