Re: Thoughts on Special Functions sinc_pi and sinhc_pi

From: Hubert HOLIN (Hubert.Holin_at_[hidden])
Date: 2001-05-19 17:28:30

Paris (U.E.), le 20/05/2001

--- In boost_at_y..., Daryle Walker <darylew_at_m...> wrote:
> These are from the Special Function library currently under review.
> 
> First Issue: Template-based Template Parameters
> 
> My compiler, CodeWarrior Pro 5.3/Mac, can't handle function templates that
> have template-based template parameters at all.  I had to comment out the
> second versions of both functions to get the code to compile.  We would have
> to #define BOOST_NO_TEMPLATE_BASED_FUNCTION_TEMPLATE_PARAMETERS in
> <boost/config.hpp> to make sure some compilers can survive.  With the
> various problems with templates that occur with the common compilers, why
> depend on the rarest feature, template-based template parameters?

        Things work fine with CWPro 6.1 . Will presumably work fine with 
6.2 and onwards...

> Second Issue: Too General?
> 
> These problematic versions are supposed to be shortcuts for defining sinc_pi
> and sinhc_pi for complex, quaterions, octonions, and the like.  They assume
> that any kind of U<T> defines a numeric type with a vector-like algebra of
> components T.  Some templates violate that, like boost::rational.  I know
> that's not the kind of type you expect to use with sinc_pi, but another
> numeric template may come along that defines a floating type, but doesn't
> define a vector algebra.  That (hypothetical) class would have to take the
> burden of defining custom sinc_pi and sinhc_pi function templates to avoid
> being matched with your second sinc_pi and sinhc_pi.  It could be better to
> avoid that by making your quaterions and octonions take the burden instead
> by defining custom sinc_pi and sinhc_pi function templates in their
> respective headers.  This would have to be the workaround for compilers that
> can't handle the problematic versions, anyway.  (For std::complex, where you
> can't make a custom function template version, maybe use the "functor class
> template used by a function template" idiom and specialize std::complex's
> version of the functor.)

        These classes and functions are designed for number crunshing, in 
various domains of application. If the types they are built upon do not 
behave like numbers, all bets are off (and one might wonder what this 
use might mean...).

> Third Issue: Testing
> 
> There is a minor testing issue, since the problematic versions are not
> tested within the Special Function's test file.

        The "problematic" versions are tested in the quaternion and 
octonion test files.

> -- 
> Daryle Walker
> Mac, Internet, and Video Game Junkie
> darylew AT mac DOT com

        Hubert Holin
        Atari (user) refugee
        Hubert.Holin_at_[hidden], hubert_holin_at_[hidden]