Class Subsequence

    • Constructor Detail

      • Subsequence

        public Subsequence()
    • Method Detail

      • getItemType

        public ItemType getItemType​(TypeHierarchy th)
        Determine the data type of the items in the sequence
        Overrides:
        getItemType in class SystemFunction
        Parameters:
        th - the type hierarchy cache
        Returns:
        the type of the argument
      • computeSpecialProperties

        public int computeSpecialProperties()
        Get the static properties of this expression (other than its type). The result is bit-significant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.
        Overrides:
        computeSpecialProperties in class SystemFunction
        Returns:
        the special properties, as a bit-significant integer
      • optimize

        public Expression optimize​(ExpressionVisitor visitor,
                                   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.

        Overrides:
        optimize in class SystemFunction
        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)