Class IdentityComparison

All Implemented Interfaces:
Serializable, SourceLocator, Container, Expression, InstructionInfoProvider

public final class IdentityComparison extends BinaryExpression
IdentityComparison: a boolean expression that compares two nodes for equals, not-equals, greater-than or less-than based on identity and document ordering
See Also:
  • Constructor Details

    • IdentityComparison

      public IdentityComparison(Expression p1, int op, Expression p2)
      Create an identity comparison identifying the two operands and the operator
      Parameters:
      p1 - the left-hand operand
      op - the operator, as a token returned by the Tokenizer (e.g. Token.LT)
      p2 - the right-hand operand
  • Method Details

    • setGenerateIdEmulation

      public void setGenerateIdEmulation(boolean flag)
      Set flag to indicate different empty-sequence behavior when emulating comparison of two generate-id's
    • typeCheck

      public Expression typeCheck(StaticContext env, ItemType contextItemType) throws XPathException
      Type-check the expression
      Specified by:
      typeCheck in interface Expression
      Overrides:
      typeCheck in class BinaryExpression
      Parameters:
      env - the static context of the expression
      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
    • evaluateItem

      public Item evaluateItem(XPathContext context) throws XPathException
      Evaluate the expression
      Specified by:
      evaluateItem in interface Expression
      Overrides:
      evaluateItem in class ComputedExpression
      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
    • effectiveBooleanValue

      public boolean effectiveBooleanValue(XPathContext context) throws XPathException
      Description copied from class: ComputedExpression
      Get the effective boolean value of the expression. This returns false if the value is the empty sequence, a zero-length string, a number equal to zero, or the boolean false. Otherwise it returns true.
      Specified by:
      effectiveBooleanValue in interface Expression
      Overrides:
      effectiveBooleanValue in class ComputedExpression
      Parameters:
      context - The context in which the expression is to be evaluated
      Returns:
      the effective boolean value
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression
    • getItemType

      public ItemType getItemType(TypeHierarchy th)
      Determine the data type of the expression
      Parameters:
      th -
      Returns:
      Type.BOOLEAN