Package net.sf.saxon.expr

Class CompareToIntegerConstant

    • Constructor Detail

      • CompareToIntegerConstant

        public CompareToIntegerConstant​(Expression operand,
                                int operator,
                                long comparand)

    • Method Detail

      • 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 interface Expression
        Overrides:
        getImplementationMethod in class ComputedExpression

      • simplify

        public Expression simplify​(StaticContext env)
                    throws XPathException
        Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation does nothing.
        Specified by:
        simplify in interface Expression
        Overrides:
        simplify in class ComputedExpression
        Parameters:
        env - the static context
        Returns:
        the simplified expression
        Throws:
        XPathException - if an error is discovered during expression rewriting

      • promote

        public Expression promote​(PromotionOffer offer)
                   throws XPathException
        Offer promotion for this subexpression. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. By default the offer is not accepted - this is appropriate in the case of simple expressions such as constant values and variable references where promotion would give no performance advantage. This method is always called at compile time.
        Specified by:
        promote in interface Expression
        Overrides:
        promote in class ComputedExpression
        Parameters:
        offer - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression
        Returns:
        if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression
        Throws:
        XPathException - if any error is detected

      • computeDependencies

        public int computeDependencies()
        Compute the dependencies of an expression, as the union of the dependencies of its subexpressions. (This is overridden for path expressions and filter expressions, where the dependencies of a subexpression are not all propogated). This method should be called only once, to compute the dependencies; after that, getDependencies should be used.
        Overrides:
        computeDependencies in class ComputedExpression
        Returns:
        the depencies, as a bit-mask

      • iterateSubExpressions

        public java.util.Iterator iterateSubExpressions()
        Get the immediate sub-expressions of this expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.
        Specified by:
        iterateSubExpressions in interface Expression
        Overrides:
        iterateSubExpressions in class ComputedExpression
        Returns:
        an iterator containing the sub-expressions of this expression

      • replaceSubExpression

        public boolean replaceSubExpression​(Expression original,
                                    Expression replacement)
        Replace one subexpression by a replacement subexpression
        Specified by:
        replaceSubExpression in interface Container
        Overrides:
        replaceSubExpression in class ComputedExpression
        Parameters:
        original - the original subexpression
        replacement - the replacement subexpression
        Returns:
        true if the original subexpression is found

      • evaluateItem

        public Item evaluateItem​(XPathContext context)
                  throws XPathException
        Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.
        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
        Throws:
        XPathException - if any dynamic error occurs evaluating the expression

      • effectiveBooleanValue

        public boolean effectiveBooleanValue​(XPathContext context)
                              throws XPathException
        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
        Throws:
        XPathException - if any dynamic error occurs evaluating the expression

      • typeCheck

        public Expression typeCheck​(StaticContext env,
                            ItemType contextItemType)
                     throws XPathException
        Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.

        This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

        This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.

        If the implementation returns a value other than "this", then it is required to ensure that the parent pointer and location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.

        Specified by:
        typeCheck in interface Expression
        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:
        StaticError - if an error is discovered during this phase (typically a type error)
        XPathException

      • optimize

        public Expression optimize​(Optimizer opt,
                           StaticContext env,
                           ItemType contextItemType)
                    throws XPathException
        Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.

        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.

        Specified by:
        optimize in interface Expression
        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:
        StaticError - if an error is discovered during this phase (typically a type error)
        XPathException

      • getItemType

        public ItemType getItemType​(TypeHierarchy th)
        Determine the data type of the expression, if possible. All expression return sequences, in general; this method determines the type of the items within the sequence, assuming that (a) this is known in advance, and (b) it is the same for all items in the sequence.

        This method should always return a result, though it may be the best approximation that is available at the time.

        Specified by:
        getItemType in interface Expression
        Parameters:
        th -
        Returns:
        a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)

      • display

        public void display​(int level,
                    java.io.PrintStream out,
                    Configuration config)
        Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
        Specified by:
        display in interface Expression
        Parameters:
        level - indentation level for this expression
        out - Output destination
        config -

      • getSingletonOperator

        public int getSingletonOperator()
        Get the primitive (singleton) operator used: one of Token.FEQ, Token.FNE, Token.FLT, Token.FGT, Token.FLE, Token.FGE
        Specified by:
        getSingletonOperator in interface ComparisonExpression

      • convertsUntypedToOther

        public boolean convertsUntypedToOther()
        Determine whether untyped atomic values should be converted to the type of the other operand
        Specified by:
        convertsUntypedToOther in interface ComparisonExpression
        Returns:
        true if untyped values should be converted to the type of the other operand, false if they should be converted to strings.