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+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtXmlPatterns module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights. These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+//
+// W A R N I N G
+// -------------
+//
+// This file is not part of the Qt API. It exists purely as an
+// implementation detail. This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+
+#ifndef Patternist_NoneType_H
+#define Patternist_NoneType_H
+
+#include "qatomictype_p.h"
+#include "qsequencetype_p.h"
+
+QT_BEGIN_HEADER
+
+QT_BEGIN_NAMESPACE
+
+namespace QPatternist
+{
+
+ /**
+ * @short Represents the special <tt>none</tt> type.
+ *
+ * @ingroup Patternist_types
+ * @see <a href="http://www.w3.org/TR/xquery-semantics/#sec_content_models">XQuery 1.0 and
+ * XPath 2.0 Formal Semantics, 2.4.3 Content models</a>
+ * @see <a href="http://www.w3.org/TR/xquery-semantics/#sec_fnerror">XQuery 1.0 and XPath 2.0
+ * Formal Semantics, 7.2.9 The fn:error function</a>
+ * @author Frans Englich <frans.englich@nokia.com>
+ */
+ class NoneType : public ItemType,
+ public SequenceType
+ {
+ public:
+ typedef QExplicitlySharedDataPointer<NoneType> Ptr;
+
+ virtual bool itemMatches(const Item &item) const;
+ virtual bool xdtTypeMatches(const ItemType::Ptr &other) const;
+
+ /**
+ * @returns always "none". That is, no namespace prefix
+ */
+ virtual QString displayName(const NamePool::Ptr &np) const;
+
+ /**
+ * @note The semantical meaning of this type's item type can
+ * surely be discussed. The function is provided due to
+ * it being mandated by the SequenceType base class.
+ *
+ * @returns always 'this' since NoneType is also an ItemType
+ */
+ virtual ItemType::Ptr itemType() const;
+
+ /**
+ * @note The semantical meaning of this type's cardinality
+ * can surely be discussed. The function is provided due to
+ * it being mandated by the SequenceType base class.
+ *
+ * @returns always Cardinality::zeroOrMore()
+ */
+ virtual Cardinality cardinality() const;
+
+ /**
+ * @returns always @c false
+ */
+ virtual bool isAtomicType() const;
+
+ /**
+ * This can be thought to be a weird function for this type(none). There
+ * is no atomized type for none, perhaps the best from a conceptual perspective
+ * would be to return @c null.
+ *
+ * This function returns BuiltinTypes::xsAnyAtomicType because
+ * the generic type checking code inserts an Atomizer in the AST
+ * when an error() function(or other node which has type none) is part of
+ * an operator expression(value/general comparison, arithmetics). The Atomizer
+ * returns the atomizedType() of its child, and by here returning xsAnyAtomicType,
+ * static operator lookup is postponed to runtime. Subsequently, expressions like error()
+ * works properly with other XPath expressions.
+ */
+ virtual ItemType::Ptr atomizedType() const;
+
+ /**
+ * @returns always @c false
+ */
+ virtual bool isNodeType() const;
+
+ /**
+ * @returns always item()
+ */
+ virtual ItemType::Ptr xdtSuperType() const;
+
+ /**
+ * @returns always @p other. The none type can be thought as
+ * disappearing when attempting to find the union of it and
+ * another type.
+ */
+ virtual const ItemType &operator|(const ItemType &other) const;
+
+ protected:
+
+ friend class CommonSequenceTypes;
+ NoneType();
+ };
+}
+
+QT_END_NAMESPACE
+
+QT_END_HEADER
+
+#endif