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//

//  W A R N I N G

//  -------------

//

// This file is not part of the Qt API.  It exists purely as an

// implementation detail.  This header file may change from version to

// version without notice, or even be removed.

//

// We mean it.

#ifndef Patternist_ExpressionSequence_H

#define Patternist_ExpressionSequence_H

#include "qunlimitedcontainer_p.h"

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

namespace QPatternist

{

    /**

     * @short Implements the comma(",") operator, the sequence constructor.

     *

     * For example, the expression <tt>alpha, beta</tt> evaluates to a sequence

     * containing the items the nodetest @c alpha evaluates to, concatenated

     * with the items the nodetest @c beta evaluates to.

     *

     * @see <a href="http://www.w3.org/TR/xpath20/#construct_seq">XML Path Language

     * (XPath) 2.0, 3.3.1 Constructing Sequences</a>

     * @author Frans Englich <frans.englich@nokia.com>

     * @ingroup Patternist_expressions

     */

    class ExpressionSequence : public UnlimitedContainer

    {

    public:

        /**

         * Creates an ExpressionSequence with the operands @p operands. @p operands

         * must contain two or more Expression instances.

         */

        ExpressionSequence(const Expression::List &operands);

        virtual Item::Iterator::Ptr evaluateSequence(const DynamicContext::Ptr &) const;

        /**

         * Forwards the call to its children.

         */

        virtual void evaluateToSequenceReceiver(const DynamicContext::Ptr &context) const;

        virtual SequenceType::List expectedOperandTypes() const;

        virtual SequenceType::Ptr staticType() const;

        /**

         * Removes any empty sequences, typically "()", from its list of children. If

         * after that rewrite has no children, it rewrites itself to the CommonValues::empty;

         * if it has only one, it rewrites to the child.

         *

         * This optimization is not very usable by itself, but potentially becomes effective after other

         * optimizations have rewritten themselves into empty sequences. Thus,

         * saving memory consumption and runtime overhead.

         */

        virtual Expression::Ptr compress(const StaticContext::Ptr &context);

        inline Item::Iterator::Ptr mapToSequence(const Expression::Ptr &,

                                                 const DynamicContext::Ptr &) const;

        virtual Expression::Ptr typeCheck(const StaticContext::Ptr &context,

                                          const SequenceType::Ptr &reqType);

        /**

         * @returns Expression::DisableElimination, plus the union

         * of all this ExpressionSequence's children's properties. If any child

         * does not have IsEvaluated, it is removed from the result.

         */

        virtual Expression::Properties properties() const;

        virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const;

        virtual ID id() const;

    private:

        typedef QExplicitlySharedDataPointer<const ExpressionSequence> ConstPtr;

    };

}

QT_END_NAMESPACE

QT_END_HEADER

#endif