sub.hpp

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// $Id$
# ifndef CPPAD_CORE_SUB_HPP
# define CPPAD_CORE_SUB_HPP

/* --------------------------------------------------------------------------
CppAD: C++ Algorithmic Differentiation: Copyright (C) 2003-16 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 CppAD namespace
namespace CppAD {

template <class Base>
AD<Base> operator - (const AD<Base> &left , const AD<Base> &right)
{
     // compute the Base part
     AD<Base> result;
     result.value_  = left.value_ - right.value_;
     CPPAD_ASSERT_UNKNOWN( Parameter(result) );

     // check if there is a recording in progress
     local::ADTape<Base>* tape = AD<Base>::tape_ptr();
     if( tape == CPPAD_NULL )
          return result;
     tape_id_t tape_id = tape->id_;

     // tape_id cannot match the default value for tape_id_; i.e., 0
     CPPAD_ASSERT_UNKNOWN( tape_id > 0 );
     bool var_left  = left.tape_id_  == tape_id;
     bool var_right = right.tape_id_ == tape_id;

     if( var_left )
     {    if( var_right )
          {    // result = variable - variable
               CPPAD_ASSERT_UNKNOWN( local::NumRes(local::SubvvOp) == 1 );
               CPPAD_ASSERT_UNKNOWN( local::NumArg(local::SubvvOp) == 2 );

               // put operand addresses in tape
               tape->Rec_.PutArg(left.taddr_, right.taddr_);
               // put operator in the tape
               result.taddr_ = tape->Rec_.PutOp(local::SubvvOp);
               // make result a variable
               result.tape_id_ = tape_id;
          }
          else if( IdenticalZero(right.value_) )
          {    // result = variable - 0
               result.make_variable(left.tape_id_, left.taddr_);
          }
          else
          {    // result = variable - parameter
               CPPAD_ASSERT_UNKNOWN( local::NumRes(local::SubvpOp) == 1 );
               CPPAD_ASSERT_UNKNOWN( local::NumArg(local::SubvpOp) == 2 );

               // put operand addresses in tape
               addr_t p = tape->Rec_.PutPar(right.value_);
               tape->Rec_.PutArg(left.taddr_, p);
               // put operator in the tape
               result.taddr_ = tape->Rec_.PutOp(local::SubvpOp);
               // make result a variable
               result.tape_id_ = tape_id;
          }
     }
     else if( var_right )
     {    // result = parameter - variable
          CPPAD_ASSERT_UNKNOWN( local::NumRes(local::SubpvOp) == 1 );
          CPPAD_ASSERT_UNKNOWN( local::NumArg(local::SubpvOp) == 2 );

          // put operand addresses in tape
          addr_t p = tape->Rec_.PutPar(left.value_);
          tape->Rec_.PutArg(p, right.taddr_);
          // put operator in the tape
          result.taddr_ = tape->Rec_.PutOp(local::SubpvOp);
          // make result a variable
          result.tape_id_ = tape_id;
     }
     return result;
}

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

} // END CppAD namespace

# endif