Re: [boost] [Math/nextafter] A question of naming functions...

From: Johan Råde (rade_at_[hidden])
Date: 2008-05-02 01:55:00

Fernando Cacciola wrote:
> Johan Råde wrote:
>> John Maddock wrote:
>>> Johan Råde wrote:
>>>>>>> floatdistance(lhs, rhs)?
>>>>>> Would adding an underscore be nicer:
>>>>>>
>>>>>> FPT float_distance(FPT lhs, FPT rhs);
>>>> How about discrete_distance?
>>> That's not bad at all actually,
>>>
>>> Thanks, John.
>> To me the word distance suggests an unsigned quantity.
>>
> Same here, but...
> 
>> Maybe discrete_difference?
>>
> The word difference in the context of a numerical operation suggests a 
> numerical difference, so I feel that distance suits better here.
> 
> I like "representation_distance". To me it says exactly what it is. And I 
> would even call it "rep_distance" since 'rep' is a fairly common 
> abbreviation.
> 
> Anyway, don't we want to also have the 'cousin' function: 
> "representation_advance", such that:
> 
> representation_advance(x,representation_distance(x,y)) == y
> 
> always holds for any x,y?
> 
> That identity makes it clear that the distance is signed.
> 
> Best

Hmm, the concept we are discussing is related
to the set of possible values of a floating point number type,
but not necessarily to the representation of these values.

Also, if we calculate the xxx_distance between a positive
and a negative number, do we count positive and negative zero
separately? I suppose not. The name representation_distance suggests that we might.

--Johan