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| |
| // |
| // 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 <private/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 |
| |
| #endif |