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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 // |
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43 // W A R N I N G |
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44 // ------------- |
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45 // |
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46 // This file is not part of the Qt API. It exists purely as an |
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47 // implementation detail. This header file may change from version to |
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48 // version without notice, or even be removed. |
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49 // |
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50 // We mean it. |
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51 |
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52 #ifndef Patternist_FirstItemPredicate_H |
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53 #define Patternist_FirstItemPredicate_H |
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54 |
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55 #include "qsinglecontainer_p.h" |
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56 |
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57 QT_BEGIN_HEADER |
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58 |
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59 QT_BEGIN_NAMESPACE |
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60 |
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61 namespace QPatternist |
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62 { |
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63 /** |
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64 * @short A predicate that always selects the first item from its sequence. |
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65 * |
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66 * FirstItemPredicate corresponds exactly to the predicate |
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67 * in the expression <tt>input[1]</tt>. |
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68 * |
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69 * @author Frans Englich <frans.englich@nokia.com> |
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70 * @ingroup Patternist_expressions |
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71 */ |
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72 class FirstItemPredicate : public SingleContainer |
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73 { |
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74 public: |
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75 /** |
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76 * Creates a FirstItemPredicate that filters @p source. |
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77 */ |
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78 FirstItemPredicate(const Expression::Ptr &source); |
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79 |
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80 /** |
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81 * @returns the first item, if any, from evaluating the source expression. |
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82 */ |
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83 virtual Item evaluateSingleton(const DynamicContext::Ptr &) const; |
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84 |
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85 /** |
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86 * @returns a list containing one CommonSequenceTypes::ZeroOrMoreItems instance. |
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87 */ |
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88 virtual SequenceType::List expectedOperandTypes() const; |
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89 |
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90 /** |
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91 * @returns a SequenceType where the item type is the same as the source expression |
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92 * and where the cardinality is either Cardinality::zeroOrOne() or Cardinality::exactlyOne(), |
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93 * depending on the source expression. |
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94 */ |
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95 virtual SequenceType::Ptr staticType() const; |
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96 virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const; |
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97 |
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98 /** |
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99 * Rewrites <tt>expression[1][1]</tt> into <tt>expression[1]</tt>. |
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100 */ |
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101 virtual Expression::Ptr compress(const StaticContext::Ptr &context); |
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102 |
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103 /** |
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104 * @returns always IDFirstItemPredicate. |
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105 */ |
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106 virtual ID id() const; |
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107 }; |
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108 } |
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109 |
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110 QT_END_NAMESPACE |
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111 |
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112 QT_END_HEADER |
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113 |
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114 #endif |