Re: [Boost-users] Range library suggestion

24 Jan 2013

      On 1/24/2013 3:59 AM, boost-users-request-at-lists.boost.org |Boost/Allow to home| wrote:
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I just added my second metafunction of the form is_range_of_X<T> for use
with enable_if, and although the first one took some fiddleing to pass
both compilers I was using, the second was a clone of the first with the
name and type changed. So it really ought to be a general purpose
is_range_of metafunction.
I assume it it's simply something like
is_same::type,
Whatever>
I ended up with:

    template 
    struct is_range_of_MYTHING2 : boost::mpl::false_ { };

    template <typename T>
    struct is_range_of_MYTHING2 {
        typedef typename boost::range_value<T>::type val_type; // chokes here if T is not
    a range
        typedef typename is_convertible::type type;
        };
    template <typename T>
    struct is_range_of_MYTHING : is_range_of_MYTHING2
        { };

I'm familiar enough with type_traits, but not with all of Boost MPL.  Is eval_if a 
lazy-evaluation for short circuiting the AND of the two tests?

---John

Re: [Boost-users] Range library suggestion

John M. Dlugosz