编译错误C2440,boost odeint中有make\u dense\u输出

ublas::vector<std::complex<double>> 具有“密集输出”,但编译时使用 只要runge\u kutta\u dopri5步进器。

#include <iostream>
#include <complex>
#include <boost/numeric/ublas/blas.hpp>
#include <boost/numeric/ublas/vector.hpp>
#include <boost/numeric/ublas/vector_proxy.hpp>
#include <boost/numeric/ublas/assignment.hpp>
#include <boost/numeric/ublas/matrix.hpp>
#include <boost/numeric/ublas/io.hpp>
#include <boost/numeric/odeint.hpp>

using namespace boost::numeric::odeint;
namespace bnu = boost::numeric::ublas;

typedef bnu::vector<std::complex< double >> state_type;

struct solver_test
{
    state_type & m_a;
    solver_test(state_type& a): m_a(a) { }

    void operator()(const state_type &x, state_type &dxdt, double t) const
    {
        // dummy!
        dxdt = element_prod(x, m_a);
    }
};

struct observer
{
    std::vector<double> & m_tm;
    std::vector<state_type> &  m_out;

    observer(std::vector<double>& tm, std::vector<state_type> & out)
        :m_tm(tm), m_out(out) { }

    template< class State >
    void operator()(const State &x, double t) const
    {
        m_tm.push_back(t);
        m_out.push_back(x);
    }
};

int main(int argc, char **argv)
{
    std::vector<double> tm;
    std::vector<state_type> out;
    state_type a_vec(10);
    std::fill_n(a_vec.begin(), 10, std::complex<double>(1.0, 0.5));

    state_type noise(10); 
    std::fill_n(noise.begin(), 10, std::complex<double>(1.5, 1.5));

    const double dt = 0.1;

    typedef runge_kutta_dopri5<state_type> dp_stepper_type;

    integrate_const(make_dense_output(1.0e-6, 1.0e-3, dp_stepper_type()),
        solver_test(a_vec), noise, 0.0, 10.0, dt, observer(tm, out));

    // This works
    //integrate_const(dp_stepper_type(),
    //  solver_test(a_vec), noise, 0.0, 10.0, dt, observer(tm, out));

    return 0;
}

我错过了什么?