Re: [boost] GSOC 2013

Subject: Re: [boost] GSOC 2013
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2013-04-22 00:28:55

Le 20/04/13 06:14, Michael Marcin a écrit :
> On 4/19/2013 7:15 PM, Vicente J. Botet Escriba wrote:
>> Le 18/04/13 15:39, Dmitriy Gorbel a écrit :
>>> I want to provide my proposal to the Boost community.
>>>
>>> Please, lets discuss it! I will be grateful for your reviews and 
>>> advices.
>>> How can I improve it?
>>> I appreciate any feedback you may have.
>>>
>>> proposal_Dmitriy_Gorbel.pdf
>>> <http://boost.2283326.n4.nabble.com/file/n4645577/proposal_Dmitriy_Gorbel.pdf> 
>>>
>>>
>>
>> <snip very good feedback>
>>
>
> There is a typo: The range must be *grater* then the resolution
>
> I don't understand your types.
>
> cardinal<16> 0 <= n <= 65536
>
> This seems to be a 16 bit unsigned type but requires 17 bits to store 
> this range. It should probably be 0 <= n <= 65535.
>
> integral<4> -16 <= n <= 16
>
> Similar here this seem to be a 5 it signed integer but requires 6 bits 
> to store this range. It should probably be -16 <= n <= 15.
>
> nonnegative<8,-4> -256 < n < 256 in increments of 2^-4 = 1/16
>
> I don't understand how a type nonnegative can store values in (-256,0).
>
>
> negatable<16,-8> -65536 < n < 65536 in increments of 2^-8
>  = 1/ 256
>
> This seems close to a fixed point type as I'm used to seeing it. 
> Although again the ranges seem wrong.
>
> I'm much more accustom to seeing fixed point number specified as 
> <Magnitude bits, Fractional Bits> i.e. <16,8> instead of <16,-8>.
> Still this representation makes sense because it specifies both 
> parameters in terms 2^x. It also supports something like <17,1> to 
> give a 16 bit type that has the range [-131072, 131071] in increments 
> of 2.
>
> Still it might be surprising to those familiar with the more common 
> fixed-point notation.
>
>
Dmitriy,
what is your opinion about this?

Best,
Vicente