Class IdentityComparison

  • All Implemented Interfaces:
    java.io.Serializable, javax.xml.transform.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:
    Serialized Form
    • Constructor Detail

      • 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 Detail

      • 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:
        StaticError - if an error is discovered during this phase (typically a type error)
        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