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46 // This file is not part of the Qt API. It exists purely as an
47 // implementation detail. This header file may change from version to
48 // version without notice, or even be removed.
52 #ifndef Patternist_ExpressionSequence_H
53 #define Patternist_ExpressionSequence_H
55 #include <private/qunlimitedcontainer_p.h>
64 * @short Implements the comma(",") operator, the sequence constructor.
66 * For example, the expression <tt>alpha, beta</tt> evaluates to a sequence
67 * containing the items the nodetest @c alpha evaluates to, concatenated
68 * with the items the nodetest @c beta evaluates to.
70 * @see <a href="http://www.w3.org/TR/xpath20/#construct_seq">XML Path Language
71 * (XPath) 2.0, 3.3.1 Constructing Sequences</a>
72 * @author Frans Englich <frans.englich@nokia.com>
73 * @ingroup Patternist_expressions
75 class ExpressionSequence : public UnlimitedContainer
79 * Creates an ExpressionSequence with the operands @p operands. @p operands
80 * must contain two or more Expression instances.
82 ExpressionSequence(const Expression::List &operands);
84 virtual Item::Iterator::Ptr evaluateSequence(const DynamicContext::Ptr &) const;
87 * Forwards the call to its children.
89 virtual void evaluateToSequenceReceiver(const DynamicContext::Ptr &context) const;
91 virtual SequenceType::List expectedOperandTypes() const;
92 virtual SequenceType::Ptr staticType() const;
95 * Removes any empty sequences, typically "()", from its list of children. If
96 * after that rewrite has no children, it rewrites itself to the CommonValues::empty;
97 * if it has only one, it rewrites to the child.
99 * This optimization is not very usable by itself, but potentially becomes effective after other
100 * optimizations have rewritten themselves into empty sequences. Thus,
101 * saving memory consumption and runtime overhead.
103 virtual Expression::Ptr compress(const StaticContext::Ptr &context);
105 inline Item::Iterator::Ptr mapToSequence(const Expression::Ptr &,
106 const DynamicContext::Ptr &) const;
108 virtual Expression::Ptr typeCheck(const StaticContext::Ptr &context,
109 const SequenceType::Ptr &reqType);
111 * @returns Expression::DisableElimination, plus the union
112 * of all this ExpressionSequence's children's properties. If any child
113 * does not have IsEvaluated, it is removed from the result.
115 virtual Expression::Properties properties() const;
116 virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const;
117 virtual ID id() const;
119 typedef QExplicitlySharedDataPointer<const ExpressionSequence> ConstPtr;