[Boost-users] [lambda] Can I use lambda::bind to a functor with a parametric return type?

Subject: [Boost-users] [lambda] Can I use lambda::bind to a functor with a parametric return type?
From: Jesse Perla (jesseperla_at_[hidden])
Date: 2009-08-28 13:18:17

Thanks for the rapid response on the previous question.  Now for my real
question:

I am using an autodifferentiation library and want to use lambda's bind, but
still return a generic type.  Is this possible?

Here is the  function I wrote :

struct test_function_impl
{
    //result_of supprt
    template<typename Sig>
    struct result;
    template<typename This, typename Arg1, typename Arg2>
    struct result<This(Arg1, Arg2)> {
        typedef typename boost::remove_reference<Arg1>::type::value_type
            type;
    };

    template<typename Vector, typename IntT>
    typename Vector::value_type //The type in the vector... can be a double
or AD type
    operator()(const Vector& x, IntT y) const{
        return x[0] * x[0] + y;
    }
};

The function works on its own, and now std::tr1::result_of seems to work as
well.

However,   I cannot bind to this:
using namespace boost::lambda;
    ublas::bounded_vector<double, 1> x;
    x[0] = 1.0;
    int int_value = 1;

//THIS FAILS!  Not sure if lambda's bind is using result_of?  Obviously,
can't use the ret<> approach here.
   auto f = bind(test_function_impl(), _1, int_value);

Does lambda support this usage, or should I turn to Phoenix (if so, I am
recognizing a trend here).

-Jesse