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Diffstat (limited to 'src/xmlpatterns/expr/qunaryexpression_p.h')
| -rw-r--r-- | src/xmlpatterns/expr/qunaryexpression_p.h | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/src/xmlpatterns/expr/qunaryexpression_p.h b/src/xmlpatterns/expr/qunaryexpression_p.h new file mode 100644 index 0000000..70a29ad --- /dev/null +++ b/src/xmlpatterns/expr/qunaryexpression_p.h @@ -0,0 +1,114 @@ +/**************************************************************************** +** +** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). +** Contact: Qt Software Information (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 qt-sales@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_UnaryExpression_H +#define Patternist_UnaryExpression_H + +QT_BEGIN_HEADER + +QT_BEGIN_NAMESPACE + +#include "qarithmeticexpression_p.h" + +namespace QPatternist +{ + /** + * @short Implements XPath 2.0 unary expression, <tt>(-|+)ValueExpr</tt>. + * + * UnaryExpression is implemented by rewriting the expression <tt>operator [expr]</tt> + * to the ArithmeticExpression <tt>0 operator [expr]</tt>. For example, the expression + * <tt>+3</tt> becomes <tt>0 + 3</tt>, and <tt>-nodetest</tt> becomes <tt>0 - nodetest</tt>. + * + * On top of that expression ArithmeticExpression does the usual type + * checking conversion. The only thing this class do, is to overide + * evaluateSingleton() and calls Numeric::toNegated(). The reason this + * UnaryExpression is needed at all and that <tt>0 - [expr]</tt> is + * insufficent is that <tt>0 - xs:double(0)</tt> needs to return -0, + * instead of 0. I know no other difference. + * + * In most cases the constant propagation optimization rewrites UnaryExpression into + * a value, an instance of a sub-class of the Numeric class, wrapped with + * Literal. + * + * Beyond the mathematical implication the unary expression have, it also + * have the significant effect that it may invoke type promotion or that an expression + * may contain a type error. For example, the expression "+'a string'" contains a type error, since + * no unary operator is defined for @c xs:string. This is the reason why the '+' unary + * operator isn't ignored. + * + * @see <a href="http://www.w3.org/TR/xpath20/#id-arithmetic">XML Path Language + * (XPath) 2.0, 3.4 Arithmetic Expressions</a> + * @see <a href="http://www.w3.org/TR/xpath-functions/#func-numeric-unary-plus">XQuery 1.0 and XPath + * 2.0 Functions and Operators, 6.2.7 op:numeric-unary-plus</a> + * @see <a href="http://www.w3.org/TR/xpath-functions/#func-numeric-unary-minus">XQuery 1.0 and XPath + * 2.0 Functions and Operators, 6.2.8 op:numeric-unary-minus</a> + * @author Frans Englich <fenglich@trolltech.com> + * @ingroup Patternist_expressions + */ + class UnaryExpression : public ArithmeticExpression + { + public: + UnaryExpression(const AtomicMathematician::Operator op, + const Expression::Ptr &operand, + const StaticContext::Ptr &context); + + virtual Item evaluateSingleton(const DynamicContext::Ptr &context) const; + + private: + Q_DISABLE_COPY(UnaryExpression) + }; +} + +QT_END_NAMESPACE + +QT_END_HEADER + +#endif |