Class CastExpression

    • Constructor Detail

      • CastExpression

        public CastExpression​(Expression source,
                              AtomicType target,
                              boolean allowEmpty)
        Create a cast expression
        Parameters:
        source - expression giving the value to be converted
        target - the type to which the value is to be converted
        allowEmpty - true if the expression allows an empty sequence as input, producing an empty sequence as output. If false, an empty sequence is a type error.
    • Method Detail

      • isPossibleCast

        public static boolean isPossibleCast​(int source,
                                             int target)
        Determine whether casting from a source type to a target type is possible
        Parameters:
        source - a primitive type (one that has an entry in the casting table)
        target - another primitive type
        Returns:
        true if the entry in the casting table is either "Y" (casting always succeeds) or "M" (casting allowed but may fail for some values)
      • getTargetPrimitiveType

        public AtomicType getTargetPrimitiveType()
        Get the primitive base type of the target type of the cast
        Returns:
        the primitive type of the target type
      • getTargetType

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

        public boolean allowsEmpty()
        Ask whether the expression accepts an empty sequence as input (producing an empty sequence as output)
        Returns:
        true if an empty sequence is accepted
      • targetIsDerived

        public boolean targetIsDerived()
        Ask whether the target type is a derived type (not a primitive type)
        Returns:
        true if the target type is a derived type
      • isUpCast

        public boolean isUpCast()
        Ask whether this is a cast to a supertype of the original type
        Returns:
        true if this is an upcast. This means the value stays unchanged and only the type label changes
      • 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)
      • getItemType

        public ItemType getItemType​(TypeHierarchy th)
        Get the static type of the 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
      • equals

        public boolean equals​(java.lang.Object other)
        Is this expression the same as another expression?
        Overrides:
        equals in class UnaryExpression
      • toString

        public java.lang.String toString()
        The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax
        Overrides:
        toString in class UnaryExpression
      • 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
      • castStringToQName

        public static AtomicValue castStringToQName​(java.lang.CharSequence operand,
                                                    AtomicType targetType,
                                                    StaticContext env)
                                             throws XPathException
        Evaluate the "pseudo-cast" of a string literal to a QName or NOTATION value. This can only happen at compile time
        Parameters:
        operand - the value to be converted
        targetType - the type to which it is to be converted
        env - the static context
        Returns:
        the QName or NOTATION value that results from casting the string to a QName. This will either be a QNameValue or a derived AtomicValue derived from QName or NOTATION
        Throws:
        XPathException