# include <cppad/cppad.hpp>


bool Var2Par(void)
{     bool ok = true;
     using CppAD::AD;
     using CppAD::Value;
     using CppAD::Var2Par;

     // domain space vector
     size_t n = 2;
     CPPAD_TESTVECTOR(AD<double>) x(n);
     x[0] = 3.;
     x[1] = 4.;

     // 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[1] * Var2Par(x[0]);    // same as y[0] = -x[1] * 3.;

     // cannot call Value(x[j]) or Value(y[0]) here (currently variables)
     ok &= ( Value( Var2Par(x[0]) ) == 3. );
     ok &= ( Value( Var2Par(x[1]) ) == 4. );
     ok &= ( Value( Var2Par(y[0]) ) == -12. );

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

     // can call Value(x[j]) or Value(y[0]) here (currently parameters)
     ok &= (Value(x[0]) ==  3.);
     ok &= (Value(x[1]) ==  4.);
     ok &= (Value(y[0]) == -12.);

     // evaluate derivative of y w.r.t x
     CPPAD_TESTVECTOR(double) w(m);
     CPPAD_TESTVECTOR(double) dw(n);
     w[0] = 1.;
     dw   = f.Reverse(1, w);
     ok  &= (dw[0] == 0.);  // derivative of y[0] w.r.t x[0] is zero
     ok  &= (dw[1] == -3.); // derivative of y[0] w.r.t x[1] is 3

     return ok;
}