# include <cppad/cppad.hpp>

bool UnaryPlus(void)
{     bool ok = true;
     using CppAD::AD;


     // domain space vector
     size_t n = 1;
     CPPAD_TESTVECTOR(AD<double>) x(n);
     x[0]      = 3.;

     // declare independent variables and start tape recording
     CppAD::Independent(x);

     // range space vector
     size_t m = 1;
     CPPAD_TESTVECTOR(AD<double>) y(m);
     y[0] = + x[0];

     // create f: x -> y and stop tape recording
     CppAD::ADFun<double> f(x, y);

     // check values
     ok &= ( y[0] == 3. );

     // forward computation of partials w.r.t. x[0]
     CPPAD_TESTVECTOR(double) dx(n);
     CPPAD_TESTVECTOR(double) dy(m);
     size_t p = 1;
     dx[0]    = 1.;
     dy       = f.Forward(p, dx);
     ok      &= ( dy[0] == 1. );   // dy[0] / dx[0]

     // reverse computation of dertivative of y[0]
     CPPAD_TESTVECTOR(double)  w(m);
     CPPAD_TESTVECTOR(double) dw(n);
     w[0] = 1.;
     dw   = f.Reverse(p, w);
     ok &= ( dw[0] == 1. );       // dy[0] / dx[0]

     // use a VecAD<Base>::reference object with unary plus
     CppAD::VecAD<double> v(1);
     AD<double> zero(0);
     v[zero] = x[0];
     AD<double> result = + v[zero];
     ok     &= (result == y[0]);

     return ok;
}