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** This file is part of the QtXmlPatterns module of the Qt Toolkit.
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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_NodeComparison_H
#define Patternist_NodeComparison_H
#include "qpaircontainer_p.h"
QT_BEGIN_HEADER
QT_BEGIN_NAMESPACE
namespace QPatternist
{
/**
* @short Implements the node comparison operators \>\>, \<\<, and @c is.
*
* @see XML Path Language
* (XPath) 2.0, 3.5.3 QXmlNodeModelIndex Comparisons
* @author Frans Englich
* @ingroup Patternist_expressions
*/
class Q_AUTOTEST_EXPORT NodeComparison : public PairContainer
{
public:
NodeComparison(const Expression::Ptr &operand1,
const QXmlNodeModelIndex::DocumentOrder op,
const Expression::Ptr &operand2);
virtual Item evaluateSingleton(const DynamicContext::Ptr &) const;
virtual bool evaluateEBV(const DynamicContext::Ptr &) const;
virtual SequenceType::List expectedOperandTypes() const;
virtual QXmlNodeModelIndex::DocumentOrder operatorID() const;
/**
* If any operator is the empty sequence, the NodeComparison rewrites
* into that, since the empty sequence is always the result in that case.
*/
virtual Expression::Ptr compress(const StaticContext::Ptr &context);
/**
* @returns either CommonSequenceTypes::ZeroOrOneBoolean or
* CommonSequenceTypes::ExactlyOneBoolean depending on the static
* cardinality of its operands.
*/
virtual SequenceType::Ptr staticType() const;
/**
* Determines the string representation for a node comparison operator.
*
* @returns
* - "<<" if @p op is Precedes
* - ">>" if @p op is Follows
* - "is" if @p op is Is
*/
static QString displayName(const QXmlNodeModelIndex::DocumentOrder op);
virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const;
private:
enum Result
{
Empty,
True,
False
};
inline Result evaluate(const DynamicContext::Ptr &context) const;
const QXmlNodeModelIndex::DocumentOrder m_op;
};
}
QT_END_NAMESPACE
QT_END_HEADER
#endif