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/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** 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 either Technology Preview License Agreement or the
** Beta Release License Agreement.
**
** 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 1.0, 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.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at http://www.qtsoftware.com/contact.
** $QT_END_LICENSE$
**
****************************************************************************/
#include "qcommonsequencetypes_p.h"
#include "qgenericsequencetype_p.h"
#include "qfirstitempredicate_p.h"
QT_BEGIN_NAMESPACE
using namespace QPatternist;
FirstItemPredicate::FirstItemPredicate(const Expression::Ptr &source) : SingleContainer(source)
{
}
Item FirstItemPredicate::evaluateSingleton(const DynamicContext::Ptr &context) const
{
/* If our operand allows the empty sequence, this function can return Item(), otherwise
* it returns the first item. As simple as that. */
return m_operand->evaluateSequence(context)->next();
}
SequenceType::Ptr FirstItemPredicate::staticType() const
{
const SequenceType::Ptr t(m_operand->staticType());
return makeGenericSequenceType(t->itemType(), t->cardinality().toWithoutMany());
}
Expression::Ptr FirstItemPredicate::compress(const StaticContext::Ptr &context)
{
const Expression::Ptr me(SingleContainer::compress(context));
if(me != this)
return me;
if(m_operand->is(IDFirstItemPredicate))
m_operand = m_operand->operands().first();
return me;
}
SequenceType::List FirstItemPredicate::expectedOperandTypes() const
{
SequenceType::List result;
result.append(CommonSequenceTypes::ZeroOrMoreItems);
return result;
}
ExpressionVisitorResult::Ptr FirstItemPredicate::accept(const ExpressionVisitor::Ptr &visitor) const
{
return visitor->visit(this);
}
Expression::ID FirstItemPredicate::id() const
{
return IDFirstItemPredicate;
}
QT_END_NAMESPACE
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