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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_AtomicComparator_H

#define Patternist_AtomicComparator_H

#include <QFlags>

#include "qitem_p.h"

#include "qatomictypedispatch_p.h"

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

class QString;

namespace QPatternist

{

    /**

     * @short Base class for classes responsible of comparing two atomic values.

     *

     * This class is also known as the AtomicParrot.

     *

     * @ingroup Patternist_xdm

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

     */

    class Q_AUTOTEST_EXPORT AtomicComparator : public AtomicTypeVisitorResult

    {

    public:

        AtomicComparator();

        virtual ~AtomicComparator();

        typedef QExplicitlySharedDataPointer<AtomicComparator> Ptr;

        /**

         * Identifies operators used in value comparisons.

         *

         * The enum values are bit-significant.

         *

         * @see <a href="http://www.w3.org/TR/xpath20/#id-value-comparisons">W3C XML Path

         * Language (XPath) 2.0, 3.5.1 Value Comparisons</a>

         */

        enum Operator

        {

            /**

             * Operator <tt>eq</tt> and <tt>=</tt>.

             */

            OperatorEqual           = 1,

            /**

             * Operator <tt>ne</tt> and <tt>!=</tt>.

             */

            OperatorNotEqual        = 1 << 1,

            /**

             * Operator <tt>gt</tt> and <tt>\></tt>.

             */

            OperatorGreaterThan     = 1 << 2,

            /**

             * Operator <tt>lt</tt> and <tt>\<</tt>.

             */

            OperatorLessThan        = 1 << 3,

            /**

             * One of the operators we use for sorting. The only difference from

             * OperatorLessThan is that it sees NaN as ordered and smaller than

             * other numbers.

             */

            OperatorLessThanNaNLeast    = 1 << 4,

            /**

             * One of the operators we use for sorting. The only difference from

             * OperatorLessThanLeast is that it sees NaN as ordered and larger than

             * other numbers.

             */

            OperatorLessThanNaNGreatest    = 1 << 5,

            /**

             * Operator <tt>ge</tt> and <tt>\>=</tt>.

             */

            OperatorGreaterOrEqual  = OperatorEqual | OperatorGreaterThan,

            /**

             * Operator <tt>le</tt> and <tt>\<=</tt>.

             */

            OperatorLessOrEqual     = OperatorEqual | OperatorLessThan

        };

        typedef QFlags<Operator> Operators;

        /**

         * Signifies the result of a value comparison. This is used for value comparisons,

         * and in the future likely also for sorting.

         *

         * @see <a href="http://www.w3.org/TR/xpath20/#id-value-comparisons">W3C XML Path

         * Language (XPath) 2.0, 3.5.1 Value Comparisons</a>

         */

        enum ComparisonResult

        {

            LessThan     = 1,

            Equal        = 2,

            GreaterThan  = 4,

            Incomparable = 8

        };

        /**

         * Compares @p op1 and @p op2 and determines the relationship between the two. This

         * is used for sorting and comparisons. The implementation performs an assert crash,

         * and must therefore be re-implemented if comparing the relevant values should be

         * possible.

         *

         * @param op1 the first operand

         * @param op the operator. How a comparison is carried out shouldn't depend on what the

         * operator is, but in some cases it is of interest.

         * @param op2 the second operand

         */

        virtual ComparisonResult compare(const Item &op1,

                                         const AtomicComparator::Operator op,

                                         const Item &op2) const;

        /**

         * Determines whether @p op1 and @p op2 are equal. It is the same as calling compare()

         * and checking whether the return value is Equal, but since comparison testing is such

         * a common operation, this specialized function exists.

         *

         * @returns true if @p op1 and @p op2 are equal.

         *

         * @param op1 the first operand

         * @param op2 the second operand

         */

        virtual bool equals(const Item &op1,

                            const Item &op2) const = 0;

        /**

         * Identifies the kind of comparison.

         */

        enum ComparisonType

        {

            /**

             * Identifies a general comparison; operator @c =, @c >, @c <=, and so on.

             */

            AsGeneralComparison = 1,

            /**

             * Identifies a value comparison; operator @c eq, @c lt, @c le, and so on.

             */

            AsValueComparison

        };

        /**

         * Utility function for getting the lexical representation for

         * the comparison operator @p op. Depending on the @p type argument,

         * the string returned is either a general comparison or a value comparison

         * operator.

         *

         * @param op the operator which the display name should be determined for.

         * @param type signifies whether the returned display name should be for

         * a value comparison or a general comparison. For example, if @p op is

         * OperatorEqual and @p type is AsValueComparision, "eq" is returned.

         */

        static QString displayName(const AtomicComparator::Operator op,

                                   const ComparisonType type);

    };

    Q_DECLARE_OPERATORS_FOR_FLAGS(AtomicComparator::Operators)

}

QT_END_NAMESPACE

QT_END_HEADER

#endif