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/****************************************************************************
**
** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the QtXmlPatterns module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Digia. For licensing terms and
** conditions see http://qt.digia.com/licensing. For further information
** use the contact form at http://qt.digia.com/contact-us.
**
** 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, Digia gives you certain additional
** rights. These rights are described in the Digia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
//
// 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
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