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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_FirstItemPredicate_H
#define Patternist_FirstItemPredicate_H
#include "qsinglecontainer_p.h"
QT_BEGIN_HEADER
QT_BEGIN_NAMESPACE
namespace QPatternist
{
/**
* @short A predicate that always selects the first item from its sequence.
*
* FirstItemPredicate corresponds exactly to the predicate
* in the expression <tt>input[1]</tt>.
*
* @author Frans Englich <frans.englich@nokia.com>
* @ingroup Patternist_expressions
*/
class FirstItemPredicate : public SingleContainer
{
public:
/**
* Creates a FirstItemPredicate that filters @p source.
*/
FirstItemPredicate(const Expression::Ptr &source);
/**
* @returns the first item, if any, from evaluating the source expression.
*/
virtual Item evaluateSingleton(const DynamicContext::Ptr &) const;
/**
* @returns a list containing one CommonSequenceTypes::ZeroOrMoreItems instance.
*/
virtual SequenceType::List expectedOperandTypes() const;
/**
* @returns a SequenceType where the item type is the same as the source expression
* and where the cardinality is either Cardinality::zeroOrOne() or Cardinality::exactlyOne(),
* depending on the source expression.
*/
virtual SequenceType::Ptr staticType() const;
virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const;
/**
* Rewrites <tt>expression[1][1]</tt> into <tt>expression[1]</tt>.
*/
virtual Expression::Ptr compress(const StaticContext::Ptr &context);
/**
* @returns always IDFirstItemPredicate.
*/
virtual ID id() const;
};
}
QT_END_NAMESPACE
QT_END_HEADER
#endif
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