Re: [boost] Review Request: Switch

From: Steven Watanabe (steven_at_[hidden])
Date: 2007-02-19 14:38:08

AMDG

David Abrahams <dave <at> boost-consulting.com> writes:

> 
> Steven Watanabe <steven <at> providere-consulting.com> writes:
> 
> > AMDG
> >
> >     I am requesting a formal review of my switch_ function template.
> > The implementation docs and tests are available in the vault.
> > http://tinyurl.com/yvssgx
> 
> Should this be part of a more general metaprogramming library
> containing "runtime construct generators?"  I can imagine such
> generators as overload_set, while_loop, if_statement...
> 

What would overload_set do?

while_loop.  Is this what you had in mind?

template<bool>
struct while_impl;

template<>
struct while_impl<true> {
    template<class Condition, class F, class T>
    struct apply {
        typedef typename F::template result<T>::type result;
        typedef typename while_impl<
            mpl::apply<Condition, result>::type::value
        >::template apply<Condition, F, result> next;
        typedef typename next::type type;
        static type value(F f, T& t) {
            result r(f(t));
            return(next::value(f, r));
        }
    };
};
template<>
struct while_impl<false> {
    template<class Condition, class F, class T>
    struct apply {
        typedef T type;
        static type value(F, T& t) {
            return(t);
        }
    };
};

I can't think of any use for if_statement that
isn't easier using if.

mpl::for_each already handles looping over a sequence.

In Christ,
Steven Watanabe