Package net.sf.saxon.functions

Class BooleanFn

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.FunctionCall
net.sf.saxon.functions.SystemFunction
net.sf.saxon.functions.BooleanFn
All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, Negatable, SequenceIterable, InstructionInfo, Locator
public class BooleanFn extends SystemFunction implements Negatable
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(ExpressionVisitor visitor) 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.
      Overrides:
      simplify in class FunctionCall
      Parameters:
      visitor - an expression visitor
      Returns:
      the simplified expression
      Throws:
      XPathException - if an error is discovered during expression rewriting

    • checkArguments

      public void checkArguments(ExpressionVisitor visitor) throws XPathException
      Static analysis: prevent sorting of the argument
      Overrides:
      checkArguments in class SystemFunction
      Parameters:
      visitor - the expression visitor
      Throws:
      XPathException

    • optimize

      public Expression optimize(ExpressionVisitor visitor, 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.

      Overrides:
      optimize in class SystemFunction
      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 if appropriate to optimize execution
      Throws:
      XPathException - if an error is discovered during this phase (typically a type error)

    • isNegatable

      public boolean isNegatable(ExpressionVisitor visitor)
      Check whether this specific instance of the expression is negatable
      Specified by:
      isNegatable in interface Negatable
      Returns:
      true if it is

    • negate

      public Expression negate()
      Create an expression that returns the negation of this expression
      Specified by:
      negate in interface Negatable
      Returns:
      the negated expression

    • rewriteEffectiveBooleanValue

      public static Expression rewriteEffectiveBooleanValue(Expression exp, ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
      Optimize an expression whose effective boolean value is required
      Parameters:
      exp - the expression whose EBV is to be evaluated
      visitor - an expression visitor
      contextItemType - the type of the context item for this expression
      Returns:
      an expression that returns the EBV of exp, or null if no optimization was possible
      Throws:
      XPathException - if static errors are found

    • evaluateItem

      public Item evaluateItem(XPathContext context) throws XPathException
      Evaluate the function
      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

    • effectiveBooleanValue

      public boolean effectiveBooleanValue(XPathContext c) throws XPathException
      Evaluate the effective boolean value
      Overrides:
      effectiveBooleanValue in class Expression
      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