Re: [boost] [fusion][ping] how to initialize a container of non-const references to objects, from a container of objects

From: Stjepan Rajko (stipe_at_[hidden])
Date: 2007-07-04 18:08:09

On 6/26/07, Stjepan Rajko <stipe_at_[hidden]> wrote:
> On 6/26/07, dan marsden <danmarsden_at_[hidden]> wrote:
> >
> > Does the attached code, using transform_view do what you need? I'm not comfortable adding non const ctors to vector for a few reasons, so I'd prefer this approach if possible.
> >
>
> This works great, thanks!  I did try a transform_view approach after I

Found a case where it doesn't compile - adapting your example to how
I'm using it:

    typedef fusion::vector<int, int> vec;
    vec v(1,2);
    fusion::transform_view<vec, make_ref> t(v, make_ref());
    fusion::vector<int &, int &> vec_of_references(t); // this works
fine, exactly what I need

However, if I change this to:

    typedef fusion::vector<> vec;
    vec v;
    fusion::transform_view<vec, make_ref> t(v, make_ref());
    fusion::vector<> vec_of_references(t); // does not compile

The problem is that since vec_of_references is a vector of size 0 then
it can't initialize from the transform_view because vector0 has no
constructors defined (so only copy constructible).

For sake of consistency, would it be possible to add a templated
constructor to vector0 that could take a fusion sequence and do
nothing with it?  I'm using this from a templated class and it would
be helpful if I didn't have to specially treat the size 0 case.

Or, perhaps there is another simple solution I'm missing... :-)

Thanks!

Stjepan