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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_ExpressionSequence_H
51#define Patternist_ExpressionSequence_H
52
53#include <private/qunlimitedcontainer_p.h>
54
55QT_BEGIN_NAMESPACE
56
57namespace QPatternist
58{
59 /**
60 * @short Implements the comma(",") operator, the sequence constructor.
61 *
62 * For example, the expression <tt>alpha, beta</tt> evaluates to a sequence
63 * containing the items the nodetest @c alpha evaluates to, concatenated
64 * with the items the nodetest @c beta evaluates to.
65 *
66 * @see <a href="http://www.w3.org/TR/xpath20/#construct_seq">XML Path Language
67 * (XPath) 2.0, 3.3.1 Constructing Sequences</a>
68 * @author Frans Englich <frans.englich@nokia.com>
69 * @ingroup Patternist_expressions
70 */
71 class ExpressionSequence : public UnlimitedContainer
72 {
73 public:
74 /**
75 * Creates an ExpressionSequence with the operands @p operands. @p operands
76 * must contain two or more Expression instances.
77 */
78 ExpressionSequence(const Expression::List &operands);
79
80 virtual Item::Iterator::Ptr evaluateSequence(const DynamicContext::Ptr &) const;
81
82 /**
83 * Forwards the call to its children.
84 */
85 virtual void evaluateToSequenceReceiver(const DynamicContext::Ptr &context) const;
86
87 virtual SequenceType::List expectedOperandTypes() const;
88 virtual SequenceType::Ptr staticType() const;
89
90 /**
91 * Removes any empty sequences, typically "()", from its list of children. If
92 * after that rewrite has no children, it rewrites itself to the CommonValues::empty;
93 * if it has only one, it rewrites to the child.
94 *
95 * This optimization is not very usable by itself, but potentially becomes effective after other
96 * optimizations have rewritten themselves into empty sequences. Thus,
97 * saving memory consumption and runtime overhead.
98 */
99 virtual Expression::Ptr compress(const StaticContext::Ptr &context);
100
101 inline Item::Iterator::Ptr mapToSequence(const Expression::Ptr &,
102 const DynamicContext::Ptr &) const;
103
104 virtual Expression::Ptr typeCheck(const StaticContext::Ptr &context,
105 const SequenceType::Ptr &reqType);
106 /**
107 * @returns Expression::DisableElimination, plus the union
108 * of all this ExpressionSequence's children's properties. If any child
109 * does not have IsEvaluated, it is removed from the result.
110 */
111 virtual Expression::Properties properties() const;
112 virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const;
113 virtual ID id() const;
114 private:
115 typedef QExplicitlySharedDataPointer<const ExpressionSequence> ConstPtr;
116 };
117}
118
119QT_END_NAMESPACE
120
121#endif
122

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