Re: [boost] [binary-int] pre-release available

From: Matt Calabrese (rivorus_at_[hidden])
Date: 2005-09-05 04:11:07

On 9/5/05, Paul Mensonides <pmenso57_at_[hidden]> wrote:
> 
> Yes, you are right. I was thinking about actually reading the binary 
> digits and
> *computing* the result. In other words, I was thinking about the 
> completely
> general approach rather than leveraging the compatible base property of
> hexadecimal (or octal) and binary. However, the reason that I looked at it 
> from
> that perspective is because it is possible to do arbitrary-precision 
> arithmetic
> with the preprocessor (Chaos does it, for example), and I actually use 
> binary
> literals as an example in the docs. With such arbitrary-precision support, 
> you
> can read numbers in any base--hence my overlooking the obvious solution. 
> :)

I really must take a look at Chaos sometime.
On 9/5/05, Paul Mensonides <pmenso57_at_[hidden]> wrote:

> And that doesn't really matter. Binary literals, AFAICT, are rarely useful 
> for
> expressing actual numbers so much as sets of flags.

Yeah, that's pretty much the conclusion I've come to as well. 

On 9/5/05, Paul Mensonides <pmenso57_at_[hidden]> wrote:

> Well, my only excuse for this is that I'd have to check the length of the
> sequence beforehand (or at least that it is less than two elements)--which 
> takes
> time. Fixed in the CVS.

Great.

On 9/5/05, Paul Mensonides <pmenso57_at_[hidden]> wrote:

> > Also note that I only allowed values which are 4 binary
> > digits long. This was just a design choice as I believe it
> > would be confusing having nibbles in the middle that have
> > under 4 digits.
> 
> Note that one of the common uses of binary literals is as packed 
> representations
> of several values. It isn't all that unusual to have a representation 
> where the
> length in bits of each part are arbitrary. If I were you, I would allow 
> such
> usage, but then you can't do a simple, direct mapping. You'd have to 
> convert
> the input to (e.g.) a sequence of bits first, and the break it up into a 
> mapping
> to hexadecimal digits. One of the advantages to doing binary literals with 
> the
> preprocessor is that you *can* do this. The template mechanism cannot
> distinguish between 0001 and 01, but the preprocessor can. (Of course, it
> becomes unreasonable to allow bit groups that are larger than a byte.)

Yeah, I think I will do that. I also wanted to keep 4-bit sequences for 
clarity and to prevent people from making subtle mistakes (accidentally 
writing 7 1s instead of 8 1s, or something like that isn't too unreasonable 
and can be tough for a programmer to notice), however the more I think about 
it, the more I agree that I should allow representations as you describe, 
since the desire truely is there and it's not horribly difficult to provide 
the functionality.
 
On 9/5/05, Paul Mensonides <pmenso57_at_[hidden]> wrote:

> Allowing "1010 110" and having it mean "1010 0110" isn't just
> confusing, it's an abomination.

Yeah, and that's another thing that really bothered me about the template 
implementation. Using the preprocessor gets rid this. I must go, but I will 
update tomorrow. It's after 5:00 AM here and I have yet to sleep. Thanks for 
the feedback and suggestions.

-- 
-Matt Calabrese