AAutomatic.h

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#ifndef OPAL_AAutomatic_HH
#define OPAL_AAutomatic_HH
 
// ------------------------------------------------------------------------
// $RCSfile: AAutomatic.h,v $
// ------------------------------------------------------------------------
// $Revision: 1.1.1.1.4.1 $
// ------------------------------------------------------------------------
// Copyright: see Copyright.readme
// ------------------------------------------------------------------------
//
// Template class: AAutomatic<T>
//
// ------------------------------------------------------------------------
//
// $Date: 2004/11/18 22:52:40 $
// $Author: jsberg $
//
// ------------------------------------------------------------------------
 
#include "AbstractObjects/Expressions.h"
#include "AbstractObjects/OpalData.h"
#include "Expressions/ADeferred.h"
 
namespace Expressions {
 
    // Template class AAutomatic
    // ----------------------------------------------------------------------
    //  An automatic expression is marked as unknown and registered in a list
    //  when it is created.  When its value is required, it is evaluated,
    //  marked as known, and the new value is cached.  Whenever a new
    //  definition is read, or an existing one is changed, the expressions
    //  are all marked as unknown. This forces a new evaluation when an
    //  exoression is used the next time.
 
    template <class T>
    class AAutomatic : public ADeferred<T> {
    public:
        //  From array of expressions.
        explicit AAutomatic(PtrToArray<T> expr);
 
        //  From array expression.
        explicit AAutomatic(ArrayOfPtrs<T> expr);
 
        AAutomatic(const AAutomatic&);
        virtual ~AAutomatic();
 
        virtual AAutomatic<T>* clone() const;
 
        //  The resulting value is cached.
        virtual std::vector<T> evaluate();
 
        //  Mark as unknown to force re-evaluation of expression.
        virtual void invalidate();
 
    private:
        // Not implemented.
        AAutomatic();
        void operator=(const AAutomatic&);
 
        // Is the expression known ?
        mutable bool is_known;
    };
 
    // Implementation
    // ----------------------------------------------------------------------
 
    template <class T>
    AAutomatic<T>::AAutomatic(const AAutomatic<T>& rhs) : ADeferred<T>(rhs), is_known(false) {
        OpalData::getInstance()->registerExpression(this);
    }
 
    template <class T>
    AAutomatic<T>::AAutomatic(PtrToArray<T> expr) : ADeferred<T>(expr), is_known(false) {
        OpalData::getInstance()->registerExpression(this);
    }
 
    template <class T>
    AAutomatic<T>::AAutomatic(ArrayOfPtrs<T> expr) : ADeferred<T>(expr), is_known(false) {
        OpalData::getInstance()->registerExpression(this);
    }
 
    template <class T>
    AAutomatic<T>::~AAutomatic() {
        // Unlink expression from expression list.
        OpalData::getInstance()->unregisterExpression(this);
    }
 
    template <class T>
    AAutomatic<T>* AAutomatic<T>::clone() const {
        return new AAutomatic<T>(*this);
    }
 
    template <class T>
    std::vector<T> AAutomatic<T>::evaluate() {
        if (!is_known) {
            ADeferred<T>::evaluate();
            is_known = true;
        }
 
        return this->value;
    }
 
    template <class T>
    void AAutomatic<T>::invalidate() {
        is_known = false;
    }
 
}  // namespace Expressions
 
#endif  // OPAL_AAutomatic_HH