/****************************************************************************

**

** All rights reserved.

** Contact: Nokia Corporation (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 Technology Preview License Agreement accompanying

** this package.

**

** 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 1.1, included in the file LGPL_EXCEPTION.txt in this package.

**

** If you have questions regarding the use of this file, please contact

** Nokia at qt-info@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 <frans.englich@nokia.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