Re: [boost] Re: Metaprogramming: Using static const or enum?

From: Terje Slettebø (tslettebo_at_[hidden])
Date: 2003-01-09 12:44:07

>From: "David Abrahams" <dave_at_[hidden]>

> Terje Slettebø <tslettebo_at_[hidden]> writes:
>
> > And since there are techniques for making out-of-class definitions
easier
> > (and automatic), which may be instantiated if needed, like you showed,
then
> > static const seems clearly best.
>
> That's not nearly so easy to take care of if the metafunction in
> question is something like alignment_of<T> which could potentially
> have lots of values, depending on the T chosen.

In what way would this affect Paul's suggestion:

template<class T, T V> struct map_integral {
    static const T value = V;
};

template<class T, T V> const T map_integral<T, V>::value;

By the way, this could have been done with mpl::integral_c, as well,
provided the out-of-class definition is given.

Do you maybe refer to that each value may take up space in the executable,
if used in such a way that instantiation is needed? That's right, and that's
not the case for enum. Still, there are the issues for enum, as well.

Regards,

Terje