RE: [boost] Math constants for naive and gurus? - which constants do you want?

From: Paul A. Bristow (boost_at_[hidden])
Date: 2001-10-24 11:12:56

This has been proposed before by the speed freaks,
BUT it was widely felt that
is was REALLY important to be able to write

double area = pi * r * r;

Without this, the constants would just not be widely used.

But as you show, current compilers favour functions,
so Michael Kenniston [Msk_at_[hidden]] can up with his cunning scheme
(sadly too cunning for at least one compiler?)

I could produce the functions you suggest, as I did before,
but using the generator program.
But I am reluctant to add further confusion.

Do you believe that the code is invalid C++?
(Or is the compiler wrong?)

Paul

PS I am right in concluding from these assembler examples
that the code generated is not bad, but that peoples mileage
may vary.

And that comprehensive benchmarking is going to be difficult and
contentious?

> -----Original Message-----
> From: Greg Colvin [mailto:gcolvin_at_[hidden]]
> Sent: Wednesday, October 24, 2001 12:14 AM
> To: boost_at_[hidden]
> Subject: Re: [boost] Math constants for naive and gurus? - which
> constants do you want?
>
>
> > Many thanks for your work on this.  Looks promising, but may
> > be worth also producing the plain const double/float/long double files
> > as well for the time being at least?
> >
> > Paul
>
> The plain const was actually less efficient for some platforms.
>
> The only problems I see with the template function approach is
> the extra typing:
>
>     v = pi
>
> is certainly easier than
>
>     v = constant<pi_tag,double>
>
> but it is not amenable to more precise implementations.
>
> How about a compromise:
>
>     v = pi<double>()
>
> and so on for all the other constants?  I think this can be
> made to work with even the most brain-dead compilers.
>
>
>
>
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