/**************************************************************************** ** ** Copyright (C) 2016 The Qt Company Ltd. ** Contact: https://www.qt.io/licensing/ ** ** This file is part of the QtXmlPatterns module of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:LGPL$ ** Commercial License Usage ** Licensees holding valid commercial Qt licenses may use this file in ** accordance with the commercial license agreement provided with the ** Software or, alternatively, in accordance with the terms contained in ** a written agreement between you and The Qt Company. For licensing terms ** and conditions see https://www.qt.io/terms-conditions. For further ** information use the contact form at https://www.qt.io/contact-us. ** ** GNU Lesser General Public License Usage ** Alternatively, this file may be used under the terms of the GNU Lesser ** General Public License version 3 as published by the Free Software ** Foundation and appearing in the file LICENSE.LGPL3 included in the ** packaging of this file. Please review the following information to ** ensure the GNU Lesser General Public License version 3 requirements ** will be met: https://www.gnu.org/licenses/lgpl-3.0.html. ** ** GNU General Public License Usage ** Alternatively, this file may be used under the terms of the GNU ** General Public License version 2.0 or (at your option) the GNU General ** Public license version 3 or any later version approved by the KDE Free ** Qt Foundation. The licenses are as published by the Free Software ** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3 ** included in the packaging of this file. Please review the following ** information to ensure the GNU General Public License requirements will ** be met: https://www.gnu.org/licenses/gpl-2.0.html and ** https://www.gnu.org/licenses/gpl-3.0.html. ** ** $QT_END_LICENSE$ ** ****************************************************************************/ // // 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_NAMESPACE #include namespace QPatternist { /** * @short Implements XPath 2.0 unary expression, (-|+)ValueExpr. * * UnaryExpression is implemented by rewriting the expression operator [expr] * to the ArithmeticExpression 0 operator [expr]. For example, the expression * +3 becomes 0 + 3, and -nodetest becomes 0 - nodetest. * * 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 0 - [expr] is * insufficent is that 0 - xs:double(0) 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 XML Path Language * (XPath) 2.0, 3.4 Arithmetic Expressions * @see XQuery 1.0 and XPath * 2.0 Functions and Operators, 6.2.7 op:numeric-unary-plus * @see XQuery 1.0 and XPath * 2.0 Functions and Operators, 6.2.8 op:numeric-unary-minus * @author Frans Englich * @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 #endif