# include <cppad/cppad.hpp>

bool SubEq(void)
{     bool ok = true;
     using CppAD::AD;
     using CppAD::NearEqual;
     double eps99 = 99.0 * std::numeric_limits<double>::epsilon();

     // domain space vector
     size_t  n = 1;
     double x0 = .5;
     CPPAD_TESTVECTOR(AD<double>) x(n);
     x[0]      = x0;

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

     // range space vector
     size_t m = 2;
     CPPAD_TESTVECTOR(AD<double>) y(m);
     y[0] = 3. * x[0];    // initial value
     y[0] -= 2;           // AD<double> -= int
     y[0] -= 4.;          // AD<double> -= double
     y[1] = y[0] -= x[0]; // use the result of a compound assignment

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

     // check value
     ok &= NearEqual(y[0] , 3.*x0-(2.+4.+x0), eps99, eps99);
     ok &= NearEqual(y[1] ,             y[0], eps99, eps99);

     // forward computation of partials w.r.t. x[0]
     CPPAD_TESTVECTOR(double) dx(n);
     CPPAD_TESTVECTOR(double) dy(m);
     dx[0] = 1.;
     dy    = f.Forward(1, dx);
     ok   &= NearEqual(dy[0], 2., eps99, eps99);
     ok   &= NearEqual(dy[1], 2., eps99, eps99);

     // reverse computation of derivative of y[0]
     CPPAD_TESTVECTOR(double)  w(m);
     CPPAD_TESTVECTOR(double) dw(n);
     w[0]  = 1.;
     w[1]  = 0.;
     dw    = f.Reverse(1, w);
     ok   &= NearEqual(dw[0], 2., eps99, eps99);

     // use a VecAD<Base>::reference object with computed subtraction
     CppAD::VecAD<double> v(1);
     AD<double> zero(0);
     AD<double> result = 1;
     v[zero] = 2;
     result -= v[zero];
     ok     &= (result == -1);

     return ok;
}