base/ExpressionNode

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/* **-*-c++-*-**************************************************************
  Copyright (C)2002 David Jung <opensim@pobox.com>

  This program/file is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.
  
  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details. (http://www.gnu.org)
  
  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  
  $Id: ExpressionNode 1029 2004-02-11 20:45:54Z jungd $
  $Revision: 1.9 $
  $Date: 2004-02-11 15:45:54 -0500 (Wed, 11 Feb 2004) $
  $Author: jungd $
 
****************************************************************************/

#ifndef _BASE_EXPRESSIONNODE_
#define _BASE_EXPRESSIONNODE_

#include <base/base>
#include <base/ReferencedObject>
#include <base/Serializable>
#include <base/Serializer>
#include <base/Vector>


namespace base {


//
// Base class of expressions that can be evaluated with a parameter Vector
//  and differentiated, 
//

class ExpressionNode : public ReferencedObject, public Serializable
{
public:
  ExpressionNode() 
    : valueCached(false), derivCached(false) {}

  enum NodeType { Sum, Difference, Product, Quotient,
                  Negative, Constant, Variable,
                  Sine, Cosine,
                  Leaf=1024, UnaryOp = 2048, BinaryOp = 4096 };

  virtual NodeType type() const = 0; ///< get NodeType
  bool isOperator() const { return (isUnaryOp() || isBinaryOp()); }
  bool isUnaryOp()  const { return Int(type() & UnaryOp); }
  bool isBinaryOp() const { return Int(type() & BinaryOp); }
  NodeType opType() const { return NodeType(Int(type()) & Int(Leaf-1)); }

  Real evaluate(const Vector& params) const 
    { 
      if (!valueCached)
        cacheValue(params);
      return value;
    }

  ref<ExpressionNode> differentiate( Int withRespectToIndex ) const 
    {   
      if (!(derivCached && (withRespectToIndex == derivWithRespToIndex)))
        cacheDerivative(withRespectToIndex);
      if (!derivative) { Assert(derivative); }
      return derivative;
    }

  virtual String toString() const = 0;

protected:
  virtual void cacheValue(const Vector& params) const = 0; ///< perform evaluation with params and store in value (& set valueCached true)
  virtual void resetCache() const = 0; ///< set valueCached false and call resetCache() on children

  mutable bool valueCached;
  mutable Real value;

  virtual void cacheDerivative(Int withRespectToIndex) const = 0; ///< perform differentiation and cache in derivative (& set set derivCached)
  virtual void resetDerivCached() const = 0; ///< set derivCached false and call resetDerivCached() on children

  mutable bool derivCached;
  mutable Int derivWithRespToIndex;
  mutable ref<ExpressionNode> derivative;

  virtual void operationCounts(Int& addsub, Int& multdiv, Int& trig) const = 0;

  friend class BinaryOpExpression;
  friend class UnaryOpExpression;
  friend class Expression;
};


inline std::ostream& operator<<(std::ostream& out, const ExpressionNode& e) // Output
{ return (out << e.toString()); }


} // base

#endif

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