Class ValueComparison

    • Constructor Detail

      • ValueComparison

        public ValueComparison​(Expression p1,
                               int op,
                               Expression p2)
        Create a relational expression 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

      • 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.
      • setResultWhenEmpty

        public void setResultWhenEmpty​(BooleanValue value)
        Set the result to be returned if one of the operands is an empty sequence
      • getResultWhenEmpty

        public BooleanValue getResultWhenEmpty()
        Get the result to be returned if one of the operands is an empty sequence
      • typeCheck

        public Expression typeCheck​(StaticContext env,
                                    ItemType contextItemType)
                             throws XPathException
        Type-check the expression
        Specified by:
        typeCheck in interface Expression
        Overrides:
        typeCheck in class BinaryExpression
        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 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
        Overrides:
        optimize in class BinaryExpression
        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
      • negate

        public ValueComparison negate()
        Return the negation of this value comparison: that is, a value comparison that returns true() if and only if the original returns false(). The result must be the same as not(this) even in the case where one of the operands is ().
      • compare

        static boolean compare​(AtomicValue v1,
                               int op,
                               AtomicValue v2,
                               AtomicComparer collator)
                        throws DynamicError
        Compare two atomic values, using a specified operator and collation
        Parameters:
        v1 - the first operand
        op - the operator, as defined by constants such as Token.FEQ or Token.FLT
        v2 - the second operand
        collator - the Collator to be used when comparing strings
        Throws:
        DynamicError - if the values are not comparable
      • evaluateItem

        public Item evaluateItem​(XPathContext context)
                          throws XPathException
        Evaluate the expression in a given context
        Specified by:
        evaluateItem in interface Expression
        Overrides:
        evaluateItem in class ComputedExpression
        Parameters:
        context - the given context for evaluation
        Returns:
        a BooleanValue representing the result of the numeric comparison of the two operands, or null representing the empty sequence
        Throws:
        XPathException - if any dynamic error occurs evaluating the expression