Package net.sf.saxon.expr

Class InstanceOfExpression

    • Constructor Detail

      • InstanceOfExpression

        public InstanceOfExpression​(Expression source,
                            SequenceType target)
        Construct an "instance of" expression in the form "source instance of target"
        Parameters:
        source - the expression whose type is to be tested
        target - the type against which it is tested

    • Method Detail

      • getRequiredItemType

        public ItemType getRequiredItemType()
        Get the item type that we are testing for membership of
        Returns:
        the item type

      • getRequiredCardinality

        public int getRequiredCardinality()
        Get the cardinality that we are testing for membership of
        Returns:
        the required cardinality

      • typeCheck

        public Expression typeCheck​(ExpressionVisitor visitor,
                            ContextItemStaticInfo contextInfo)
                     throws XPathException
        Type-check the expression
        Overrides:
        typeCheck in class UnaryExpression
        Parameters:
        visitor - an expression visitor
        contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.
        Returns:
        the checked expression
        Throws:
        XPathException - if an error is discovered during this phase (typically a type error)

      • optimize

        public Expression optimize​(ExpressionVisitor visitor,
                           ContextItemStaticInfo contextInfo)
                    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 UnaryExpression
        Parameters:
        visitor - an expression visitor
        contextInfo - 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)

      • getImplementationMethod

        public int getImplementationMethod()
        An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.
        Specified by:
        getImplementationMethod in class Expression
        Returns:
        the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

      • equals

        public boolean equals​(java.lang.Object other)
        Is this expression the same as another expression?
        Overrides:
        equals in class UnaryExpression
        Parameters:
        other - the other operand; the result is false if this is not an Expression
        Returns:
        true if the other operand is an expression and if it can be determined that the two expressions are equivalent, in the sense that they will always return the same result.

      • computeHashCode

        protected int computeHashCode()
        get HashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.
        Overrides:
        computeHashCode in class UnaryExpression
        Returns:
        a computed hash code

      • copy

        public Expression copy​(RebindingMap rebindings)
        Copy an expression. This makes a deep copy.
        Specified by:
        copy in class Expression
        Parameters:
        rebindings - variable references that need to be rebound
        Returns:
        the copy of the original expression

      • getItemType

        public ItemType getItemType()
        Determine the data type of the result of the InstanceOf expression
        Overrides:
        getItemType in class UnaryExpression
        Returns:
        the item type of the items in the result sequence, insofar as this is known statically.

      • getStaticUType

        public UType getStaticUType​(UType contextItemType)
        Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.
        Overrides:
        getStaticUType in class Expression
        Parameters:
        contextItemType - the statically-inferred type of the context item
        Returns:
        the static item type of the expression according to the XSLT 3.0 defined rules

      • evaluateItem

        public BooleanValue evaluateItem​(XPathContext context)
                          throws XPathException
        Evaluate the expression
        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
        Evaluate the expression as a boolean
        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

      • getExpressionName

        public java.lang.String getExpressionName()
        Get a name identifying the kind of expression, in terms meaningful to a user.
        Overrides:
        getExpressionName in class Expression
        Returns:
        a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in export() output displaying the expression.

      • export

        public void export​(ExpressionPresenter out)
            throws XPathException
        Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
        Specified by:
        export in interface ExportAgent
        Overrides:
        export in class UnaryExpression
        Parameters:
        out - the expression presenter used to display the structure
        Throws:
        XPathException - if the export fails, for example if an expression is found that won't work in the target environment.

      • 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
        Returns:
        a representation of the expression as a string

      • toShortString

        public java.lang.String toShortString()
        Produce a short string identifying the expression for use in error messages
        Overrides:
        toShortString in class UnaryExpression
        Returns:
        a short string, sufficient to identify the expression

      • getStreamerName

        public java.lang.String getStreamerName()
        Get the (partial) name of a class that supports streaming of this kind of expression
        Overrides:
        getStreamerName in class Expression
        Returns:
        the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class

      • getElaborator

        public Elaborator getElaborator()
        Make an elaborator for this expression
        Overrides:
        getElaborator in class Expression
        Returns:
        a suitable elaborator