Package net.sf.saxon.expr

Class IdentityComparison

    • Constructor Detail

      • IdentityComparison

        public IdentityComparison​(Expression p1,
                          int op,
                          Expression p2)
        Create an identity comparison identifying the two operands and the operator
        Parameters:
        p1 - the left-hand operand
        op - the operator, as a token returned by the Tokenizer (e.g. Token.LT)
        p2 - the right-hand operand

    • Method Detail

      • setGenerateIdEmulation

        public void setGenerateIdEmulation​(boolean flag)
        Set flag to indicate different empty-sequence behavior when emulating comparison of two generate-id's. This is relevant when operands evaluate to an empty sequence; if both are empty, the "is" operator returns (), while the generate-id() comparison compares two empty strings, which returns true; if one is empty, the "is" operator returns (), while the generate-id() comparison returns false.
        Parameters:
        flag - true if this function is being used to compare generate-id() output

      • isGenerateIdEmulation

        public boolean isGenerateIdEmulation()
        Test the flag that indicates different empty-sequence behavior when emulating comparison of two generate-id's
        Returns:
        true if this function is being used to compare generate-id() output

      • typeCheck

        public Expression typeCheck​(ExpressionVisitor visitor,
                            ContextItemStaticInfo contextInfo)
                     throws XPathException
        Type-check the expression
        Overrides:
        typeCheck in class BinaryExpression
        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 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,
                           ContextItemStaticInfo 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 BinaryExpression
        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)

      • copy

        public Expression copy​(RebindingMap rebindings)
        Copy an expression. This makes a deep copy.
        Specified by:
        copy in class Expression
        Parameters:
        rebindings - variables that must be re-bound
        Returns:
        the copy of the original expression

      • tag

        protected java.lang.String tag()
        Get the element name used to identify this expression in exported expression format
        Overrides:
        tag in class BinaryExpression
        Returns:
        the element name used to identify this expression

      • 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
        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

      • getItemType

        public ItemType getItemType()
        Determine the data type of the expression
        Specified by:
        getItemType in class Expression
        Returns:
        Type.BOOLEAN

      • 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 static type of the context item
        Returns:
        the static item type of the expression according to the XSLT 3.0 defined rules

      • 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.

      • displayOperator

        protected java.lang.String displayOperator()
        Display the operator used by this binary expression
        Overrides:
        displayOperator in class BinaryExpression
        Returns:
        String representation of the operator (for diagnostic display only)

      • getElaborator

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