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1 /**************************************************************************** |
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2 ** |
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3 ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). |
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4 ** All rights reserved. |
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5 ** Contact: Nokia Corporation (qt-info@nokia.com) |
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6 ** |
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7 ** This file is part of the QtXmlPatterns module of the Qt Toolkit. |
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8 ** |
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9 ** $QT_BEGIN_LICENSE:LGPL$ |
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10 ** No Commercial Usage |
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11 ** This file contains pre-release code and may not be distributed. |
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12 ** You may use this file in accordance with the terms and conditions |
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13 ** contained in the Technology Preview License Agreement accompanying |
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14 ** this package. |
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15 ** |
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16 ** GNU Lesser General Public License Usage |
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17 ** Alternatively, this file may be used under the terms of the GNU Lesser |
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18 ** General Public License version 2.1 as published by the Free Software |
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19 ** Foundation and appearing in the file LICENSE.LGPL included in the |
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20 ** packaging of this file. Please review the following information to |
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21 ** ensure the GNU Lesser General Public License version 2.1 requirements |
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22 ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. |
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23 ** |
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24 ** In addition, as a special exception, Nokia gives you certain additional |
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25 ** rights. These rights are described in the Nokia Qt LGPL Exception |
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26 ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package. |
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27 ** |
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28 ** If you have questions regarding the use of this file, please contact |
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29 ** Nokia at qt-info@nokia.com. |
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30 ** |
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31 ** |
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32 ** |
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33 ** |
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34 ** |
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35 ** |
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36 ** |
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37 ** |
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38 ** $QT_END_LICENSE$ |
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39 ** |
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40 ****************************************************************************/ |
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41 |
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42 #include "qcommonsequencetypes_p.h" |
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43 #include "qgenericsequencetype_p.h" |
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44 |
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45 #include "qfirstitempredicate_p.h" |
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46 |
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47 QT_BEGIN_NAMESPACE |
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48 |
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49 using namespace QPatternist; |
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50 |
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51 FirstItemPredicate::FirstItemPredicate(const Expression::Ptr &source) : SingleContainer(source) |
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52 { |
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53 } |
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54 |
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55 Item FirstItemPredicate::evaluateSingleton(const DynamicContext::Ptr &context) const |
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56 { |
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57 /* If our operand allows the empty sequence, this function can return Item(), otherwise |
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58 * it returns the first item. As simple as that. */ |
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59 return m_operand->evaluateSequence(context)->next(); |
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60 } |
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61 |
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62 SequenceType::Ptr FirstItemPredicate::staticType() const |
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63 { |
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64 const SequenceType::Ptr t(m_operand->staticType()); |
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65 return makeGenericSequenceType(t->itemType(), t->cardinality().toWithoutMany()); |
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66 } |
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67 |
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68 Expression::Ptr FirstItemPredicate::compress(const StaticContext::Ptr &context) |
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69 { |
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70 const Expression::Ptr me(SingleContainer::compress(context)); |
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71 if(me != this) |
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72 return me; |
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73 |
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74 if(m_operand->is(IDFirstItemPredicate)) |
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75 m_operand = m_operand->operands().first(); |
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76 |
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77 return me; |
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78 } |
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79 |
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80 SequenceType::List FirstItemPredicate::expectedOperandTypes() const |
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81 { |
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82 SequenceType::List result; |
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83 result.append(CommonSequenceTypes::ZeroOrMoreItems); |
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84 return result; |
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85 } |
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86 |
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87 ExpressionVisitorResult::Ptr FirstItemPredicate::accept(const ExpressionVisitor::Ptr &visitor) const |
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88 { |
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89 return visitor->visit(this); |
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90 } |
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91 |
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92 Expression::ID FirstItemPredicate::id() const |
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93 { |
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94 return IDFirstItemPredicate; |
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95 } |
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96 |
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97 QT_END_NAMESPACE |