Class CastableExpression

    • Constructor Detail

      • CastableExpression

        public CastableExpression​(Expression source,
                                  AtomicType target,
                                  boolean allowEmpty)
        Create a "castable" expression of the form "source castable as target"
        Parameters:
        source - The source expression
        target - The type being tested against
        allowEmpty - true if an empty sequence is acceptable, that is if the expression was written as "source castable as target?"
    • Method Detail

      • getTargetType

        public AtomicType getTargetType()
        Get the target type
        Returns:
        the target type
      • allowsEmpty

        public boolean allowsEmpty()
        Determine whether the empty sequence is allowed
        Returns:
        true if an empty sequence is allowed
      • typeCheck

        public Expression typeCheck​(ExpressionVisitor visitor,
                                    ItemType contextItemType)
                             throws XPathException
        Type-check the expression
        Overrides:
        typeCheck in class UnaryExpression
        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 to perform necessary run-time type checks, and to perform other type-related optimizations
        Throws:
        XPathException - if an error is discovered during this phase (typically a type error)
      • optimize

        public Expression optimize​(ExpressionVisitor visitor,
                                   ItemType contextItemType)
                            throws XPathException
        Optimize the expression
        Overrides:
        optimize in class UnaryExpression
        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)
      • equals

        public boolean equals​(java.lang.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
        Overrides:
        getItemType in class UnaryExpression
        Parameters:
        th - the type hierarchy cache
        Returns:
        the item type of the items in the result sequence, insofar as this is known statically.
      • copy

        public Expression copy()
        Copy an expression. This makes a deep copy.
        Specified by:
        copy in class Expression
        Returns:
        the copy of the original expression
      • evaluateItem

        public Item evaluateItem​(XPathContext context)
                          throws XPathException
        Evaluate the expression
        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 context)
                                      throws XPathException
        Description copied from class: Expression
        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.
        Overrides:
        effectiveBooleanValue in class Expression
        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
      • isCastable

        public static boolean isCastable​(AtomicValue value,
                                         AtomicType targetType,
                                         XPathContext context)
        Determine whether a value is castable to a given type
        Parameters:
        value - the value to be tested
        targetType - the type to be tested against
        context - XPath dynamic context
        Returns:
        true if the value is castable to the required type
      • explain

        public void explain​(ExpressionPresenter out)
        Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
        Overrides:
        explain in class UnaryExpression
        Parameters:
        out - the expression presenter used to display the structure