Re: [boost] [mpl] float representation

From: Cromwell Enage (sponage_at_[hidden])
Date: 2005-03-24 18:02:40

--- Andy Little wrote: ---
> What is the rationale for the 4 different types
> representing rational fractions?

Presumably you mean fraction, fraction_c, rational,
and rational_c?

The fraction_c struct template is simply a
metafunction that returns a fraction type, and the
rational_c struct template returns a rational type. 
(Or was it the other way around?)  The fraction struct
template covers a smaller range of numbers than the
rational struct template, but the rational struct
template models the concept of a mixed number, which
consists of a whole number part and a fraction part,
so I figured both the fraction and rational
representations were essential.  It certainly made
implementation simpler.

> What is the rationale for making the numerator and
> denominator types in fraction_c?

In an earlier version, the numerator and denominator
were defined by BOOST_STATIC_CONSTANT.  Looking
through the Integral Constant Guidelines and the MPL
source code, I read that certain compilers were likely
to complain about the very code I used to have:
BOOST_STATIC_CONSTANT before typedef statements,
fraction_c<long,7,8>::value inside macros, etc.  Not
that I have these compilers on hand, but I figured I
wasn't making this sub-library just for myself,
either, so I searched for a better representation.  Lo
and behold, Aleksey Gurtovoy created a set of
arithmetic metafunction classes that do the dirty work
for me.  I simply built on top of his work.

                              Thanks for your
interest!
                              Cromwell D. Enage

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