1 /****************************************************************************
3 ** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
4 ** Contact: http://www.qt-project.org/
6 ** This file is part of the QtXmlPatterns module of the Qt Toolkit.
8 ** $QT_BEGIN_LICENSE:LGPL$
9 ** GNU Lesser General Public License Usage
10 ** This file may be used under the terms of the GNU Lesser General Public
11 ** License version 2.1 as published by the Free Software Foundation and
12 ** appearing in the file LICENSE.LGPL included in the packaging of this
13 ** file. Please review the following information to ensure the GNU Lesser
14 ** General Public License version 2.1 requirements will be met:
15 ** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
17 ** In addition, as a special exception, Nokia gives you certain additional
18 ** rights. These rights are described in the Nokia Qt LGPL Exception
19 ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
21 ** GNU General Public License Usage
22 ** Alternatively, this file may be used under the terms of the GNU General
23 ** Public License version 3.0 as published by the Free Software Foundation
24 ** and appearing in the file LICENSE.GPL included in the packaging of this
25 ** file. Please review the following information to ensure the GNU General
26 ** Public License version 3.0 requirements will be met:
27 ** http://www.gnu.org/copyleft/gpl.html.
30 ** Alternatively, this file may be used in accordance with the terms and
31 ** conditions contained in a signed written agreement between you and Nokia.
40 ****************************************************************************/
42 #include "qcommonsequencetypes_p.h"
43 #include "qgenericsequencetype_p.h"
45 #include "qfirstitempredicate_p.h"
49 using namespace QPatternist;
51 FirstItemPredicate::FirstItemPredicate(const Expression::Ptr &source) : SingleContainer(source)
55 Item FirstItemPredicate::evaluateSingleton(const DynamicContext::Ptr &context) const
57 /* If our operand allows the empty sequence, this function can return Item(), otherwise
58 * it returns the first item. As simple as that. */
59 return m_operand->evaluateSequence(context)->next();
62 SequenceType::Ptr FirstItemPredicate::staticType() const
64 const SequenceType::Ptr t(m_operand->staticType());
65 return makeGenericSequenceType(t->itemType(), t->cardinality().toWithoutMany());
68 Expression::Ptr FirstItemPredicate::compress(const StaticContext::Ptr &context)
70 const Expression::Ptr me(SingleContainer::compress(context));
74 if(m_operand->is(IDFirstItemPredicate))
75 m_operand = m_operand->operands().first();
80 SequenceType::List FirstItemPredicate::expectedOperandTypes() const
82 SequenceType::List result;
83 result.append(CommonSequenceTypes::ZeroOrMoreItems);
87 ExpressionVisitorResult::Ptr FirstItemPredicate::accept(const ExpressionVisitor::Ptr &visitor) const
89 return visitor->visit(this);
92 Expression::ID FirstItemPredicate::id() const
94 return IDFirstItemPredicate;