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    41 

    42 //

    43 //  W A R N I N G

    44 //  -------------

    45 //

    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.

    49 //

    50 // We mean it.

    51 

    52 #ifndef Patternist_ExpressionSequence_H

    53 #define Patternist_ExpressionSequence_H

    54 

    55 #include "qunlimitedcontainer_p.h"

    56 

    57 QT_BEGIN_HEADER

    58 

    59 QT_BEGIN_NAMESPACE

    60 

    61 namespace QPatternist

    62 {

    63     /**

    64      * @short Implements the comma(",") operator, the sequence constructor.

    65      *

    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.

    69      *

    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

    74      */

    75     class ExpressionSequence : public UnlimitedContainer

    76     {

    77     public:

    78         /**

    79          * Creates an ExpressionSequence with the operands @p operands. @p operands

    80          * must contain two or more Expression instances.

    81          */

    82         ExpressionSequence(const Expression::List &operands);

    83 

    84         virtual Item::Iterator::Ptr evaluateSequence(const DynamicContext::Ptr &) const;

    85 

    86         /**

    87          * Forwards the call to its children.

    88          */

    89         virtual void evaluateToSequenceReceiver(const DynamicContext::Ptr &context) const;

    90 

    91         virtual SequenceType::List expectedOperandTypes() const;

    92         virtual SequenceType::Ptr staticType() const;

    93 

    94         /**

    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.

    98          *

    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.

   102          */

   103         virtual Expression::Ptr compress(const StaticContext::Ptr &context);

   104 

   105         inline Item::Iterator::Ptr mapToSequence(const Expression::Ptr &,

   106                                                  const DynamicContext::Ptr &) const;

   107 

   108         virtual Expression::Ptr typeCheck(const StaticContext::Ptr &context,

   109                                           const SequenceType::Ptr &reqType);

   110         /**

   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.

   114          */

   115         virtual Expression::Properties properties() const;

   116         virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const;

   117         virtual ID id() const;

   118     private:

   119         typedef QExplicitlySharedDataPointer<const ExpressionSequence> ConstPtr;

   120     };

   121 }

   122 

   123 QT_END_NAMESPACE

   124 

   125 QT_END_HEADER

   126 

   127 #endif