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39
40//
41// W A R N I N G
42// -------------
43//
44// This file is not part of the Qt API. It exists purely as an
45// implementation detail. This header file may change from version to
46// version without notice, or even be removed.
47//
48// We mean it.
49
50#ifndef Patternist_NodeComparison_H
51#define Patternist_NodeComparison_H
52
53#include <private/qpaircontainer_p.h>
54
55QT_BEGIN_NAMESPACE
56
57namespace QPatternist
58{
59
60 /**
61 * @short Implements the node comparison operators <tt>\>\></tt>, <tt>\<\<</tt>, and @c is.
62 *
63 * @see <a href="http://www.w3.org/TR/xpath20/#id-node-comparisons">XML Path Language
64 * (XPath) 2.0, 3.5.3 QXmlNodeModelIndex Comparisons</a>
65 * @author Frans Englich <frans.englich@nokia.com>
66 * @ingroup Patternist_expressions
67 */
68 class Q_AUTOTEST_EXPORT NodeComparison : public PairContainer
69 {
70 public:
71 NodeComparison(const Expression::Ptr &operand1,
72 const QXmlNodeModelIndex::DocumentOrder op,
73 const Expression::Ptr &operand2);
74
75 virtual Item evaluateSingleton(const DynamicContext::Ptr &) const;
76 virtual bool evaluateEBV(const DynamicContext::Ptr &) const;
77
78 virtual SequenceType::List expectedOperandTypes() const;
79
80 virtual QXmlNodeModelIndex::DocumentOrder operatorID() const;
81 /**
82 * If any operator is the empty sequence, the NodeComparison rewrites
83 * into that, since the empty sequence is always the result in that case.
84 */
85 virtual Expression::Ptr compress(const StaticContext::Ptr &context);
86
87 /**
88 * @returns either CommonSequenceTypes::ZeroOrOneBoolean or
89 * CommonSequenceTypes::ExactlyOneBoolean depending on the static
90 * cardinality of its operands.
91 */
92 virtual SequenceType::Ptr staticType() const;
93
94 /**
95 * Determines the string representation for a node comparison operator.
96 *
97 * @returns
98 * - "<<" if @p op is Precedes
99 * - ">>" if @p op is Follows
100 * - "is" if @p op is Is
101 */
102 static QString displayName(const QXmlNodeModelIndex::DocumentOrder op);
103
104 virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const;
105 private:
106 enum Result
107 {
108 Empty,
109 True,
110 False
111 };
112 inline Result evaluate(const DynamicContext::Ptr &context) const;
113
114 const QXmlNodeModelIndex::DocumentOrder m_op;
115
116 };
117}
118
119QT_END_NAMESPACE
120
121#endif
122

source code of qtxmlpatterns/src/xmlpatterns/expr/qnodecomparison_p.h