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# ifndef CPPAD_SUB_INCLUDED
# define CPPAD_SUB_INCLUDED

/* --------------------------------------------------------------------------
CppAD: C++ Algorithmic Differentiation: Copyright (C) 2003-07 Bradley M. Bell

CppAD is distributed under multiple licenses. This distribution is under
the terms of the 
                    Common 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 CppAD namespace
namespace CppAD {

template <class Base>
AD<Base> AD<Base>::operator -(const AD<Base> &right) const
{
        AD<Base> result;
        CPPAD_ASSERT_UNKNOWN( Parameter(result) );

        result.value_  = value_ - right.value_;

        if( Variable(*this) )
        {       if( Variable(right) )
                {       // result = variable - variable
                        CPPAD_ASSERT_KNOWN(
                                id_ == right.id_,
                                "Subtracting AD objects that are"
                                " variables on different tapes."
                        );
                        tape_this()->RecordOp(SubvvOp, 
                                result, taddr_, right.taddr_
                        );
                }
                else if( IdenticalZero(right.value_) )
                {       // result = variable - 0
                        result.make_variable(id_, taddr_);
                }
                else
                {       // result = variable - parameter
                        tape_this()->RecordOp(SubvpOp, 
                                result, taddr_, right.value_
                        );
                }
        }
        else if( Variable(right) )
        {       // result = parameter - variable
                right.tape_this()->RecordOp(SubpvOp, 
                        result, value_, right.taddr_
                );
        }

        return result;
}

// convert other cases to the case above
CPPAD_FOLD_AD_VALUED_BINARY_OPERATOR(-)


} // END CppAD namespace

# endif 

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