Package net.sf.saxon.expr

Class NegateExpression

  • All Implemented Interfaces:
    ExportAgent, Locatable, IdentityComparable, Traceable
    public class NegateExpression
extends UnaryExpression
    Negate Expression: implements the unary minus operator. This expression is initially created as an ArithmeticExpression (or in backwards compatibility mode, an ArithmeticExpression10) to take advantage of the type checking code. So we don't need to worry about type checking or argument conversion.

    • Constructor Detail

      • NegateExpression

        public NegateExpression​(Expression base)
        Create a NegateExpression
        Parameters:
        base - the expression that computes the value whose sign is to be reversed

    • Method Detail

      • setBackwardsCompatible

        public void setBackwardsCompatible​(boolean compatible)
        Set whether the expression is to be evaluated in XPath 1.0 compatibility mode
        Parameters:
        compatible - true if XPath 1.0 compatibility mode is enabled

      • isBackwardsCompatible

        public boolean isBackwardsCompatible()
        Ask whether the expression is to be evaluated in XPath 1.0 compatibility mode
        Returns:
        true if XPath 1.0 compatibility mode is enabled

      • typeCheck

        public Expression typeCheck​(ExpressionVisitor visitor,
                            ContextItemStaticInfo contextInfo)
                     throws XPathException
        Description copied from class: UnaryExpression
        Type-check the expression. Default implementation for unary operators that accept any kind of operand
        Overrides:
        typeCheck in class UnaryExpression
        Parameters:
        visitor - an expression visitor
        contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.
        Returns:
        the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
        Throws:
        XPathException - if an error is discovered during this phase (typically a type error)

      • getItemType

        public ItemType getItemType()
        Determine the data type of the expression, if this is known statically
        Overrides:
        getItemType in class UnaryExpression
        Returns:
        the item type of the items in the result sequence, insofar as this is known statically.

      • getImplementationMethod

        public int getImplementationMethod()
        An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.
        Specified by:
        getImplementationMethod in class Expression
        Returns:
        the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

      • evaluateItem

        public NumericValue evaluateItem​(XPathContext context)
                          throws XPathException
        Evaluate the expression.
        Overrides:
        evaluateItem in class Expression
        Parameters:
        context - The context in which the expression is to be evaluated
        Returns:
        the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
        Throws:
        XPathException - if any dynamic error occurs evaluating the expression

      • copy

        public Expression copy​(RebindingMap rebindings)
        Copy an expression. This makes a deep copy.
        Specified by:
        copy in class Expression
        Parameters:
        rebindings - variables that need to be re-bound
        Returns:
        the copy of the original expression

      • displayOperator

        protected java.lang.String displayOperator​(Configuration config)
        Description copied from class: UnaryExpression
        Give a string representation of the operator for use in diagnostics
        Overrides:
        displayOperator in class UnaryExpression
        Parameters:
        config - the Saxon configuration
        Returns:
        the operator, as a string

      • getExpressionName

        public java.lang.String getExpressionName()
        Get a name identifying the kind of expression, in terms meaningful to a user.
        Overrides:
        getExpressionName in class Expression
        Returns:
        a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.

      • export

        public void export​(ExpressionPresenter out)
            throws XPathException
        Description copied from class: UnaryExpression
        Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
        Specified by:
        export in interface ExportAgent
        Overrides:
        export in class UnaryExpression
        Parameters:
        out - the expression presenter used to display the structure
        Throws:
        XPathException - if the export fails, for example if an expression is found that won't work in the target environment.

      • getElaborator

        public Elaborator getElaborator()
        Make an elaborator for this expression
        Overrides:
        getElaborator in class Expression
        Returns:
        a suitable elaborator