// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later
// SPDX-FileCopyrightText: Bradley M. Bell <bradbell@seanet.com>
// SPDX-FileContributor: 2003-22 Bradley M. Bell
// ----------------------------------------------------------------------------

/*
Test the use of the special parameters zero and one with the multiply operator
*/

# include <cppad/cppad.hpp>

typedef CppAD::AD<double>      ADdouble;
typedef CppAD::AD< ADdouble > ADDdouble;

bool SubZero(void)
{
   using namespace CppAD;

   bool ok = true;

   size_t i;
   for(i = 0; i < 2; i++)
   {  // run through the cases x = 0, 1

      size_t j;
      for(j = 0; j < 2; j++)
      {  // run through the cases y = 0, 1

         CPPAD_TESTVECTOR( ADdouble ) x(1);
         x[0] = double(i);
         Independent(x);

         CPPAD_TESTVECTOR( ADDdouble ) y(1);
         y[0] = ADDdouble(j);
         Independent(y);

         CPPAD_TESTVECTOR( ADDdouble ) z(2);
         z[0]  = x[0] - y[0];
         z[1]  = y[0] - x[0];
         z[1] -= x[0];

         // f(y) = z = { x - y , y - x - x }
         ADFun< ADdouble > f(y, z);
         CPPAD_TESTVECTOR( ADdouble ) u( f.Domain() );
         CPPAD_TESTVECTOR( ADdouble ) v( f.Range() );

         // v = f(y)
         u[0] = ADdouble(j);
         v = f.Forward(0, u);

         // check value of f
         ok &= v[0] == x[0] - ADdouble(j);
         ok &= v[1] == ADdouble(j) - x[0] - x[0];

         // g(x) = f(y) = {x - y , y - x - x}
         ADFun<double> g(x, v);
         CPPAD_TESTVECTOR( double ) a( g.Domain() );
         CPPAD_TESTVECTOR( double ) b( g.Range() );

         // b = g'(x)
         a[0] = 1.;
         b = g.Forward(1, a);

         // check derivatives of g
         ok &= (b[0] == 1.);
         ok &= (b[1] == -2.);

      }
   }

   return ok;
}
