Re: boost subnamespaces proposal.

From: helmut.zeisel_at_[hidden]
Date: 2001-06-29 02:23:36

--- In boost_at_y..., Daryle Walker <darylew_at_m...> wrote:

> 
> Are we starting it now?  I guess the structure could be:
> 
> - BOOST_ROOT
>     - boost
>         - math
>             quaternion.hpp
>             octonion.hpp
>             advanced_trignometric.hpp (atanh, sinc_pi, sinhc_pi)
>             rational.hpp
>     - libs
>         - math
>             - doc
>                 quaternion.html
>                 octonion.html
>                 advanced_trignometric.html
>                 rational.html
>               index.html
>             + src
>             + test
> 

How would you handle functions that might have slightly different
implementations depending on the domain?

Look at pow(T x,I n):
it is defined for every integer n if T is
a group (e.g. x is float),
it is defined only for non-negative n if T is a monoid
(e.g. x is int),
and it is defined only for n>0 of T is a semigroup.

Similar things apply to binomial coefficients:

binom(m,n)=binom(m,m-n) if both m and n are integral,
but binom(x,n) != binom(x,x-n) (the latter is not defined)
if x is float.

One solution might be to have a

group::pow,
monoid::pow,
and semigroup::pow.

This might be easier to implement than
to have clever template specialisation techniques
the derive the respective algorithm from the template types.

Helmut