Re: [Boost-users] How to use the "type" member template pattern for using result_of?

28 Aug 2009


      AMDG

Jesse Perla wrote:
...
Take the following function:
struct test_function
{
    template
    typename Vector::value_type
    operator()(const Vector& x, IntType bound_value) const{
        return x[0] * x[0] + bound_value;
    }
};
I wasn't sure exactly how the "type" member template pattern works so that
result_of will work.
I tried the following, but can't figure out how to extract the type of the
arguments or convert to an MPL sequence?  Is there some trick I am missing?
struct test_function
{
    template<typename Args>
    struct result {
       //HOW TO CONVERT TO MPL SEQUENCE OR ANOTHER APPROACH?
        typedef typename boost::mpl::at_c::type::value_type type;
    };
template
    typename Vector::value_type //The type in the vector... can be a double
or AD type
    operator()(const Vector& x, IntType bound_value) const{
        return x[0] * x[0] + bound_value;
    }
};
struct test_function {
    template<typename Sig>
    struct result;
    template
    struct result {
        typedef typename boost::remove_reference<Arg1>::type::value_type 
type;
    };
};

In Christ,
Steven Watanabe