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

From: dherring_at_[hidden]
Date: 2008-04-30 12:25:40

On Wed, 30 Apr 2008, John Maddock wrote:

> dherring_at_[hidden] wrote:
>> On Tue, 29 Apr 2008, John Maddock wrote:
>>
>>> Folks I'm looking for some good names for some functions I'm on the
>>> brink of adding to Boost.Math (all in namespace boost::math::):
>>>
>>> T nextafter(T val, T dir)
>>> T next_greater(T val)
>>> T next_less(T val)
>>
>> Given the first name is fixed, this is a reasonable family of names;
>> though dropping the underscore would increase consistency.  However,
>> there
>> is the ambiguity whether greater/less reference zero or infinity.
>
> Not sure what you mean there, next_greater returns a value that is strictly
> greater than the argument (so always moves towards positive infinity).

I confused myself.  Standard terminology says < and > are "less than" and 
"greater than"; so your names are fine.

Still think the underscore should be dropped for consistency.

>> float x=1.0;
>> float y=2.0;
>> int d=edit_distance(x, y);
>> float z=x;
>> for(int i=0; i<d/2; i++)
>> {
>>   z=next_greater(z);
>> }
>> // Does y==(x+z)/2, given the right rounding mode?
>
> Change i<d/2 to i<2*d and yes I believe so.

That was supposed to read

// Does z==(x+y)/2?

Which I think you've answered as yes.

All of these operations apply to integers (albeit in the trivial sense 
that i and i+1 are always separated by a single gap).  Thus it might be 
nice if these operators could be applied to all numeric types, integers 
and floating-point.

Thanks,
Daniel