Re: [Boost-users] Using Boost.Fusion transform on vector<int&>

From: dan marsden (danmarsden_at_[hidden])
Date: 2007-09-12 02:22:47

Martin Ecker wrote:
>I need something like the following (somewhat contrived) example to
>work with boost::fusion::transform on a boost::fusion::vector<int&> or
>other vector types that have reference types.
>Note that the following doesn't compile.

<snip original example>

The following code allows references to pass through, as I believe you want. It just
uses a slight modification to your function object to allow it to cope with references
correctly. 

namespace
{
    struct pass_through
    {
        template<typename Sig>
        struct result;

        template<typename T>
        struct result<pass_through(T&)>
        {
            typedef T& type;
        };

        template<typename T>
        T& operator()(T& t) const
        {
            return t;
        }
    };
}

int main()
{
    typedef fusion::vector<int&> vec;
    int i = 202;
    vec v1(i);
    vec v2(fusion::transform(v1, pass_through()));

    std::cout << fusion::at_c<0>(v2) << std::endl; // Output 202
}

Is this ok for your needs?

Cheers

Dan



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