Class BooleanFn

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

public class BooleanFn extends SystemFunction
This class supports the XPath functions boolean(), not(), true(), and false()
See Also:
  • Field Details

  • Constructor Details

    • BooleanFn

      public BooleanFn()
  • Method Details

    • simplify

      public Expression simplify(StaticContext env) throws XPathException
      Simplify the function call. Default method is to simplify each of the supplied arguments and evaluate the function if all are now known.
      Specified by:
      simplify in interface Expression
      Overrides:
      simplify in class FunctionCall
      Parameters:
      env - the static context
      Returns:
      the simplified expression
      Throws:
      XPathException - if an error is discovered during expression rewriting
    • checkArguments

      public void checkArguments(StaticContext env) throws XPathException
      Static analysis: prevent sorting of the argument
      Overrides:
      checkArguments in class SystemFunction
      Throws:
      XPathException
    • optimize

      public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType) throws XPathException
      Perform optimisation of an expression and its subexpressions.

      This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

      Specified by:
      optimize in interface Expression
      Overrides:
      optimize in class FunctionCall
      Parameters:
      opt - the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.
      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 if appropriate to optimize execution
      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 function
      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 c) throws XPathException
      Evaluate the effective boolean value
      Specified by:
      effectiveBooleanValue in interface Expression
      Overrides:
      effectiveBooleanValue in class ComputedExpression
      Parameters:
      c - 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