Class CastableExpression

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

public final class CastableExpression extends UnaryExpression
Castable Expression: implements "Expr castable as atomic-type?". The implementation simply wraps a cast expression with a try/catch.
See Also:
  • Field Details

    • targetType

      AtomicType targetType
    • allowEmpty

      boolean allowEmpty
  • Constructor Details

    • CastableExpression

      public CastableExpression(Expression source, AtomicType target, boolean allowEmpty)
  • Method Details

    • simplify

      public Expression simplify(StaticContext env) throws XPathException
      Simplify the expression
      Specified by:
      simplify in interface Expression
      Overrides:
      simplify in class UnaryExpression
      Parameters:
      env - the static context
      Returns:
      the simplified expression
      Throws:
      XPathException - if an error is discovered during expression rewriting
    • typeCheck

      public Expression typeCheck(StaticContext env, ItemType contextItemType) throws XPathException
      Type-check the expression
      Specified by:
      typeCheck in interface Expression
      Overrides:
      typeCheck in class UnaryExpression
      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
    • optimize

      public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType) throws XPathException
      Optimize the expression
      Specified by:
      optimize in interface Expression
      Overrides:
      optimize in class UnaryExpression
      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:
      XPathException
    • equals

      public boolean equals(Object other)
      Is this expression the same as another expression?
      Overrides:
      equals in class UnaryExpression
    • getItemType

      public ItemType getItemType(TypeHierarchy th)
      Determine the data type of the result of the Castable expression
      Specified by:
      getItemType in interface Expression
      Overrides:
      getItemType in class UnaryExpression
      Parameters:
      th -
      Returns:
      the item type of the items in the result sequence, insofar as this is known statically.
    • computeCardinality

      public int computeCardinality()
      Description copied from class: UnaryExpression
      Determine the static cardinality. Default implementation returns the cardinality of the operand
      Overrides:
      computeCardinality in class UnaryExpression
    • computeSpecialProperties

      public int computeSpecialProperties()
      Determine the special properties of this expression
      Overrides:
      computeSpecialProperties in class UnaryExpression
      Returns:
      StaticProperty.NON_CREATIVE.
    • evaluateItem

      public Item evaluateItem(XPathContext context)
      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
    • effectiveBooleanValue

      public boolean effectiveBooleanValue(XPathContext context)
      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
    • displayOperator

      protected String displayOperator(Configuration config)
      Give a string representation of the operator for use in diagnostics
      Specified by:
      displayOperator in class UnaryExpression
      Parameters:
      config -
      Returns:
      the operator, as a string