/* $Id: sub.cpp 2506 2012-10-24 19:36:49Z bradbell $ */
/* --------------------------------------------------------------------------
CppAD: C++ Algorithmic Differentiation: Copyright (C) 2003-12 Bradley M. Bell

CppAD is distributed under multiple licenses. This distribution is under
the terms of the 
                    Eclipse Public License Version 1.0.

A copy of this license is included in the COPYING file of this distribution.
Please visit http://www.coin-or.org/CppAD/ for information on other licenses.
-------------------------------------------------------------------------- */

/*
$begin sub.cpp$$

$section AD Binary Subtraction: Example and Test$$

$index -, AD example$$
$index subtract, AD example$$
$index minus, AD example$$
$index example, subtract$$
$index test, subtract$$

$code
$verbatim%example/sub.cpp%0%// BEGIN C++%// END C++%1%$$
$$

$end
*/
// BEGIN C++
# include <cppad/cppad.hpp>

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

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

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

	AD<double> a = 2. * x[0] - 1.; // AD<double> - double
	AD<double> b = a  - 2;         // AD<double> - int
	AD<double> c = 3. - b;         // double     - AD<double> 
	AD<double> d = 4  - c;         // int        - AD<double> 

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

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

	// check value 
	ok &= NearEqual(y[0], x0-4.+3.+2.-2.*x0+1.,  1e-10 , 1e-10);

	// 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], -1., 1e-10, 1e-10);

	// reverse computation of derivative of y[0]
	CPPAD_TESTVECTOR(double)  w(m);
	CPPAD_TESTVECTOR(double) dw(n);
	w[0]  = 1.;
	dw    = f.Reverse(1, w);
	ok   &= NearEqual(dw[0], -1., 1e-10, 1e-10);

	// use a VecAD<Base>::reference object with subtraction
	CppAD::VecAD<double> v(1);
	AD<double> zero(0);
	v[zero] = b;
	AD<double> result = 3. - v[zero];
	ok     &= (result == c);

	return ok;
}

// END C++
