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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