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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_TruthPredicate_H
51 #define Patternist_TruthPredicate_H
52 
53 #include <private/qgenericpredicate_p.h>
54 
55 QT_BEGIN_NAMESPACE
56 
57 namespace QPatternist
58 {
59     /**
60      * @short A predicate which is optimized for filter expressions that
61      * are of type @c xs:boolean.
62      *
63      * @author Frans Englich <frans.englich@nokia.com>
64      * @ingroup Patternist_expressions
65      */
66     class TruthPredicate : public GenericPredicate
67     {
68     public:
69         /**
70          * Creates a TruthPredicate which filters the items from the @p sourceExpression
71          * through @p predicate.
72          *
73          * This constructor is protected. The proper way to create predicates is via the static
74          * create() function.
75          */
76         TruthPredicate(const Expression::Ptr &sourceExpression,
77                        const Expression::Ptr &predicate);
78 
mapToItem(const Item & item,const DynamicContext::Ptr & context)79         inline Item mapToItem(const Item &item, const DynamicContext::Ptr &context) const
80         {
81             Q_ASSERT_X(false, Q_FUNC_INFO, "This is practically dead code because it never gets called in GenericPredicate, "
82                                            "which binds to its own mapToItem for completely legitime reasons.");
83             if(m_operand2->evaluateEBV(context))
84                 return item;
85             else
86                 return Item();
87         }
88 
map(const Item & item,const DynamicContext::Ptr & context)89         inline Item::Iterator::Ptr map(const Item &item,
90                                        const DynamicContext::Ptr &context) const
91         {
92             Q_ASSERT_X(false, Q_FUNC_INFO, "I don't expect this function to be called, for the same reasons as above.");
93             if(m_operand2->evaluateEBV(context))
94                 return makeSingletonIterator(item);
95             else
96                 return CommonValues::emptyIterator;
97         }
98 
99         virtual SequenceType::List expectedOperandTypes() const;
100         virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const;
101     };
102 }
103 
104 QT_END_NAMESPACE
105 
106 #endif
107