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From: Fernando Cacciola (fcacciola_at_[hidden])
Date: 2001-05-17 13:27:35

----- Original Message -----
From: Matthew Austern <austern_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Thursday, May 17, 2001 3:15 PM
Subject: Re: [boost] Math Constants Library formal review results

> Fernando Cacciola wrote:
> > > But we don't have completeness. We never can.
> > >
> > > You've got sqrt(2), but not, if I'm remembering right,
> > > sqrt(3) or sqrt(5). You've got pi and e, but not, if
> > > I'm remembering right, Euler's constant (a.k.a. gamma).
> > > You don't have the zeros of the Bessel functions. And
> > > once you start including derived quantities, there's
> > > no end to it: do you include pi/2, pi/3, 2*pi, 4*pi,
> > > a/pi, pi^2...? How about e^2 (a.k.a. exp(2)), or ln(2),
> > > or ln(10)? All of those are useful.
> > >
> > > Please note: I'm not criticizing you for providing an
> > > incomplete selection of constants. You have to draw
> > > a line somewhere, and I don't know of any non-arbitrary
> > > way to draw one.
> > >
> > I addressed this before.
> > If constants are provided in a namespace -not in a struct-, there's
> > no line at all becuase constants
> > can be added freely without clutering the interface:
> There's a line because, no matter who the maintainer is,
> the time and knowledge of the maintainer is limited. Also
> because of practical problems like the length of the
> header file and the documentation, and the problem of
> coming up with useful ASCII names for each constant.
> I named a handful of transcendental constants that I've
> had occassion to use, and a few irrational numbers and
> derived quantities. I'm sure someone else would have come
> up with a different handful. I'm not seriously suggesting
> that all of the different numbers that anyone could come
> up with should be included in a constants header; I don't
> think that users would be well served by a header with
> thousands of numbers.
But I note that my proposition allows that borderline to be drawn
*naturally* (inherently unlimited set of constants or limited
time/space/resources), not arbitrarily by design.

Fernando Cacciola
Sierra s.r.l.

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