Class ForExpression

    • Constructor Detail

      • ForExpression

        public ForExpression()
        Create a "for" expression (for $x at $p in SEQUENCE return ACTION)
    • Method Detail

      • setPositionVariable

        public void setPositionVariable​(PositionVariable decl)
        Set the reference to the position variable (XQuery only)
        Parameters:
        decl - the range variable declaration for the position variable
      • getPositionVariableName

        public StructuredQName getPositionVariableName()
        Get the name of the position variable
        Returns:
        the name of the position variable ("at $p") if there is one, or null if not
      • setSlotNumber

        public void setSlotNumber​(int nr)
        Set the slot number for the range variable
        Overrides:
        setSlotNumber in class Assignation
        Parameters:
        nr - the slot number allocated to the range variable on the local stack frame. This implicitly allocates the next slot number to the position variable if there is one.
      • getRequiredSlots

        public int getRequiredSlots()
        Get the number of slots required.
        Overrides:
        getRequiredSlots in class Assignation
        Returns:
        normally 1, except for a FOR expression with an AT clause, where it is 2.
      • typeCheck

        public Expression typeCheck​(ExpressionVisitor visitor,
                                    ItemType contextItemType)
                             throws XPathException
        Type-check the expression
        Overrides:
        typeCheck in class Expression
        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 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,
                                   ItemType contextItemType)
                            throws XPathException
        Optimize the expression
        Overrides:
        optimize in class Expression
        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)
      • hasLoopingSubexpression

        public boolean hasLoopingSubexpression​(Expression child)
        Given an expression that is an immediate child of this expression, test whether the evaluation of the parent expression causes the child expression to be evaluated repeatedly
        Overrides:
        hasLoopingSubexpression in class Expression
        Parameters:
        child - the immediate subexpression
        Returns:
        true if the child expression is evaluated repeatedly
      • convertWhereToPredicate

        public Expression convertWhereToPredicate​(ExpressionVisitor visitor,
                                                  ItemType contextItemType)
                                           throws XPathException
        Convert where clause, if possible, to a predicate.
        Parameters:
        visitor - the expression visitor
        contextItemType - the item type of the context item
        Returns:
        the converted expression if modified, or null otherwise
        Throws:
        XPathException
      • copy

        public Expression copy()
        Copy an expression. This makes a deep copy.
        Specified by:
        copy in class Expression
        Returns:
        the copy of the original expression
      • markTailFunctionCalls

        public int markTailFunctionCalls​(StructuredQName qName,
                                         int arity)
        Mark tail function calls: only possible if the for expression iterates zero or one times. (This arises in XSLT/XPath, which does not have a LET expression, so FOR gets used instead)
        Overrides:
        markTailFunctionCalls in class Expression
        Parameters:
        qName - the name of the function
        arity - the arity (number of parameters) of the function
        Returns:
        0 if no tail call was found; 1 if a tail call on a different function was found; 2 if a tail recursive call was found and if this call accounts for the whole of the value.
      • extendBindingList

        protected Binding[] extendBindingList​(Binding[] in)
        Extend an array of variable bindings to include the binding(s) defined in this expression
        Overrides:
        extendBindingList in class Assignation
        Parameters:
        in - a set of variable bindings
        Returns:
        a set of variable bindings including all those supplied plus this one
      • checkPermittedContents

        public void checkPermittedContents​(SchemaType parentType,
                                           StaticContext env,
                                           boolean whole)
                                    throws XPathException
        Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type. It's always OK to say yes, since the check will be repeated at run-time. The process of checking element and attribute constructors against the content model of a complex type also registers the type of content expected of those constructors, so the static validation can continue recursively.
        Overrides:
        checkPermittedContents in class Expression
        Parameters:
        parentType - the "given complex type": the method is checking that the nodes returned by this expression are acceptable members of the content model of this type
        env - the static context
        whole - if true, we want to check that the value of this expression satisfies the content model as a whole; if false we want to check that the value of the expression is acceptable as one part of the content
        Throws:
        XPathException - if the value delivered by this expression cannot be part of the content model of the given type
      • iterateEvents

        public EventIterator iterateEvents​(XPathContext context)
                                    throws XPathException
        Deliver the result of the expression as a sequence of events.
        Overrides:
        iterateEvents in class Expression
        Parameters:
        context - The dynamic evaluation context
        Returns:
        the result of the expression as an iterator over a sequence of PullEvent objects
        Throws:
        XPathException - if a dynamic error occurs during expression evaluation
      • process

        public void process​(XPathContext context)
                     throws XPathException
        Process this expression as an instruction, writing results to the current outputter
        Overrides:
        process in class Expression
        Parameters:
        context - The dynamic context, giving access to the current node, the current variables, etc.
        Throws:
        XPathException
      • evaluatePendingUpdates

        public void evaluatePendingUpdates​(XPathContext context,
                                           PendingUpdateList pul)
                                    throws XPathException
        Evaluate an updating expression, adding the results to a Pending Update List. The default implementation of this method, which is used for non-updating expressions, throws an UnsupportedOperationException
        Overrides:
        evaluatePendingUpdates in class Expression
        Parameters:
        context - the XPath dynamic evaluation context
        pul - the pending update list to which the results should be written
        Throws:
        XPathException
      • getItemType

        public ItemType getItemType​(TypeHierarchy th)
        Determine the data type of the items returned by the expression, if possible
        Specified by:
        getItemType in class Expression
        Parameters:
        th - the type hierarchy cache
        Returns:
        one of the values Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known in advance)
      • explain

        public void explain​(ExpressionPresenter out)
        Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
        Specified by:
        explain in class Expression
        Parameters:
        out - the expression presenter used to display the structure