qt-everywhere-src-5.15.1/qtxmlpatterns/src/xmlpatterns/expr/qemptycontainer_p.h

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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_EmptyContainer_H
#define Patternist_EmptyContainer_H

#include <private/qexpression_p.h>

QT_BEGIN_NAMESPACE

namespace QPatternist
{
    /**
     * @short Base class for expressions that has no operands.
     *
     * @author Frans Englich <frans.englich@nokia.com>
     * @ingroup Patternist_expressions
     */
    class Q_AUTOTEST_EXPORT EmptyContainer : public Expression
    {
    public:
        /**
         * @returns always an empty list.
         */
        virtual Expression::List operands() const;

        /**
         * Does nothing, since sub-classes has no operands. Calling
         * it makes hence no sense, and it also results in an assert crash.
         */
        virtual void setOperands(const Expression::List &);

    protected:
        /**
         * @returns always @c true
         */
        virtual bool compressOperands(const StaticContext::Ptr &context);

        /**
         * @returns always an empty list since it has no operands.
         */
        virtual SequenceType::List expectedOperandTypes() const;

    };
}

QT_END_NAMESPACE

#endif