Class NegateExpression

All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, Locator

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.
See Also:
  • Constructor Details

    • NegateExpression

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

    • 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
    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) 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
      contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
      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(TypeHierarchy th)
      Determine the data type of the expression, if this is known statically
      Overrides:
      getItemType in class UnaryExpression
      Parameters:
      th - the type hierarchy cache
      Returns:
      the item type of the items in the result sequence, insofar as this is known statically.
    • evaluateItem

      public Item evaluateItem(XPathContext context) throws XPathException
      Evaluate the expression.
      Specified by:
      evaluateItem in interface EvaluableItem
      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()
      Copy an expression. This makes a deep copy.
      Specified by:
      copy in class Expression
      Returns:
      the copy of the original expression
    • displayOperator

      protected 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
      Returns:
      the operator, as a string