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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_CastAs_H
51#define Patternist_CastAs_H
52
53#include <private/qsinglecontainer_p.h>
54#include <private/qcastingplatform_p.h>
55
56QT_BEGIN_NAMESPACE
57
58namespace QPatternist
59{
60 /**
61 * @short Implements XPath 2.0's <tt>cast as</tt> expression.
62 *
63 * Implements the casting expression, such as <tt>'3' cast as xs:integer</tt>. This class also
64 * implements constructor functions, which are created in the ConstructorFunctionsFactory.
65 *
66 * CastAs uses CastingPlatform for carrying out the actual casting.
67 *
68 * @see <a href="http://www.w3.org/TR/xpath-functions/#casting">XQuery 1.0
69 * and XPath 2.0 Functions and Operators, 7 Casting</a>
70 * @see <a href="http://www.w3.org/TR/xpath20/#id-cast">XML Path Language
71 * (XPath) 2.0, 3.10.2 Cast</a>
72 * @author Frans Englich <frans.englich@nokia.com>
73 * @ingroup Patternist_expressions
74 */
75 class CastAs : public SingleContainer,
76 public CastingPlatform<CastAs, true /* issueError */>
77 {
78 public:
79
80 /**
81 * @todo Wrong/old documentation
82 *
83 * Creates a cast expression for the type @p name via the schema type
84 * factory @p factory. This function is used by parser when creating
85 * 'cast to' expressions, and the ConstructorFunctionsFactory, when creating
86 * constructor functions.
87 *
88 * @param targetType the type which the CastAs should cast to
89 * @param source the operand to evaluate and then cast from
90 */
91 CastAs(const Expression::Ptr &source,
92 const SequenceType::Ptr &targetType);
93
94 virtual Item evaluateSingleton(const DynamicContext::Ptr &) const;
95
96 virtual SequenceType::List expectedOperandTypes() const;
97
98 /**
99 * @returns a SequenceType where the ItemType is this CastAs's
100 * target type, as per targetType(), and the Cardinality is inferred from the
101 * source operand to reflect whether this CastAs always will evaluate to
102 * exactly-one or zero-or-one values.
103 */
104 virtual SequenceType::Ptr staticType() const;
105
106 /**
107 * Overridden in order to check that casting to an abstract type
108 * is not attempted.
109 */
110 virtual Expression::Ptr typeCheck(const StaticContext::Ptr &context,
111 const SequenceType::Ptr &reqType);
112
113 /**
114 * If the target type is the same as the source type, it is rewritten
115 * to the operand.
116 */
117 virtual Expression::Ptr compress(const StaticContext::Ptr &context);
118 virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const;
119
120 inline ItemType::Ptr targetType() const
121 {
122 return m_targetType->itemType();
123 }
124
125 inline SequenceType::Ptr targetSequenceType() const
126 {
127 return m_targetType;
128 }
129
130 private:
131 /**
132 * Performs casting to @c xs:QName. This case is special, and is always done at compile time.
133 */
134 Expression::Ptr castToQName(const StaticContext::Ptr &context) const;
135
136 const SequenceType::Ptr m_targetType;
137 };
138}
139
140QT_END_NAMESPACE
141
142#endif
143

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