Re: [boost] GSOC 2013

Subject: Re: [boost] GSOC 2013
From: Michael Marcin (mike.marcin_at_[hidden])
Date: 2013-04-20 00:14:12

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.