ADeferred.h

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#ifndef OPAL_ADeferred_HH
#define OPAL_ADeferred_HH
 
// ------------------------------------------------------------------------
// $RCSfile: ADeferred.h,v $
// ------------------------------------------------------------------------
// $Revision: 1.3.4.1 $
// ------------------------------------------------------------------------
// Copyright: see Copyright.readme
// ------------------------------------------------------------------------
//
// Template class: ADeferred<T>
//
// ------------------------------------------------------------------------
//
// $Date: 2004/11/18 22:52:40 $
// $Author: jsberg $
//
// ------------------------------------------------------------------------
 
#include <exception>
#include <iosfwd>
#include <vector>
#include "AbstractObjects/Attribute.h"
#include "AbstractObjects/Expressions.h"
#include "Expressions/AList.h"
#include "Expressions/AValue.h"
#include "Utilities/LogicalError.h"
#include "Utilities/OpalException.h"
 
namespace Expressions {
 
    // Template class ADeferred
    // ----------------------------------------------------------------------
    //  A deferred expression is always re-evaluated when its value is
    //  required.  This is notably needed to implement random generators.
 
    template <class T>
    class ADeferred : public AValue<T> {
    public:
        //  Construct empty array.
        ADeferred();
 
        //  From array expression.
        explicit ADeferred(PtrToArray<T> expr);
 
        //  From array constant.
        explicit ADeferred(const std::vector<T>& val);
 
        //  From array of scalar expressions.
        explicit ADeferred(ArrayOfPtrs<T> expr);
 
        ADeferred(const ADeferred<T>&);
        virtual ~ADeferred();
 
        virtual ADeferred<T>* clone() const;
 
        //  The expression is always re-evaluated.
        virtual std::vector<T> evaluate();
 
        virtual bool isExpression() const;
 
        virtual void print(std::ostream&) const;
 
        void setComponent(int i, const PtrToScalar<T> expr);
 
    protected:
        //  This expression is used first to evaluate all components of
        //  the expression.  Individual values may be overwritten using
        //  [b]itsOverrides[b].
        PtrToArray<T> itsLaw;
 
        //  After applying [b]itsLaw[/b] to evaluate all components, any
        //  scalar expression defined in this array is used to overwrite
        //  the corresponding component.
        ArrayOfPtrs<T> itsOverrides;
 
    private:
        // Not implemented.
        void operator=(const ADeferred<T>&);
 
        // Guard against recursive definition.
        mutable bool in_evaluation;
    };
 
    // Implementation
    // ----------------------------------------------------------------------
 
    template <class T>
    ADeferred<T>::ADeferred() : AValue<T>(), itsLaw(), itsOverrides(), in_evaluation(false) {}
 
    template <class T>
    ADeferred<T>::ADeferred(const ADeferred<T>& rhs)
        : AValue<T>(),
          itsLaw(rhs.itsLaw->clone()),
          itsOverrides(rhs.itsOverrides.size()),
          in_evaluation(false) {
        for (typename ArrayOfPtrs<T>::size_type i = 0; i < rhs.itsOverrides.size(); ++i) {
            itsOverrides[i] = rhs.itsOverrides[i]->clone();
        }
    }
 
    template <class T>
    ADeferred<T>::ADeferred(const std::vector<T>& val)
        : AValue<T>(val), itsLaw(0), itsOverrides(0), in_evaluation(false) {}
 
    template <class T>
    ADeferred<T>::ADeferred(PtrToArray<T> expr)
        : AValue<T>(), itsLaw(expr), itsOverrides(), in_evaluation(false) {}
 
    template <class T>
    ADeferred<T>::ADeferred(ArrayOfPtrs<T> expr)
        : AValue<T>(), itsLaw(), itsOverrides(expr), in_evaluation(false) {}
 
    template <class T>
    ADeferred<T>::~ADeferred() {}
 
    template <class T>
    ADeferred<T>* ADeferred<T>::clone() const {
        return new ADeferred<T>(*this);
    }
 
    template <class T>
    std::vector<T> ADeferred<T>::evaluate() {
        if (in_evaluation) {
            throw LogicalError("ADeferred::evaluate()", "Recursive expression definitions found.");
        } else {
            in_evaluation = true;
 
            try {
                if (itsLaw.isValid()) this->value = itsLaw->evaluate();
                in_evaluation = false;
                if (this->value.size() < itsOverrides.size()) {
                    this->value.resize(itsOverrides.size());
                }
 
                for (typename ArrayOfPtrs<T>::size_type i = 0; i < itsOverrides.size(); ++i) {
                    if (itsOverrides[i].isValid()) {
                        this->value[i] = itsOverrides[i]->evaluate();
                    }
                }
            } catch (OpalException& ex) {
                in_evaluation = false;
                throw LogicalError(
                        ex.where(),
                        "Evaluating expression \"" + this->getImage() + "\": " + ex.what());
            } catch (std::exception& ex) {
                in_evaluation = false;
                throw LogicalError(
                        "ADeferred::evaluate()", "Standard C++ exception while evaluating \""
                                                         + this->getImage() + "\": " + ex.what());
            } catch (...) {
                in_evaluation = false;
                throw LogicalError(
                        "ADeferred::evaluate()",
                        "Unknown exception while evaluating \"" + this->getImage() + "\": ");
            }
        }
 
        return this->value;
    }
 
    template <class T>
    bool ADeferred<T>::isExpression() const {
        return itsLaw.isValid() || (!itsOverrides.empty());
    }
 
    template <class T>
    void ADeferred<T>::print(std::ostream& os) const {
        // Print the generating law, if any.
        if (itsLaw.isValid()) itsLaw->print(os, 0);
 
        // Print the overrides.
        if (!itsOverrides.empty()) {
            os << "; overrides: {";
            typename ArrayOfPtrs<T>::const_iterator i = itsOverrides.begin();
 
            while (i != itsOverrides.end()) {
                if (i->isValid()) (*i)->print(os);
                if (++i == itsOverrides.end()) break;
                os << ',';
            }
 
            os << '}';
        }
 
        return;
    }
 
    template <class T>
    void ADeferred<T>::setComponent(int index, const PtrToScalar<T> expr) {
        while (int(itsOverrides.size()) < index) {
            itsOverrides.push_back(PtrToScalar<T>());
        }
 
        itsOverrides[index - 1] = expr;
    }
 
}  // namespace Expressions
 
#endif  // OPAL_ADeferred_HH