Class ForExpression

    • Field Detail

      • actionCardinality

        int actionCardinality
    • Constructor Detail

      • ForExpression

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

      • 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 explain() output displaying the expression.
      • 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,
                                    ExpressionVisitor.ContextItemType 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)
      • getRangeVariableCardinality

        protected int getRangeVariableCardinality()
        Get the cardinality of the range variable
        Returns:
        the cardinality of the range variable (StaticProperty.EXACTLY_ONE). Can be overridden in a subclass
      • optimize

        public Expression optimize​(ExpressionVisitor visitor,
                                   ExpressionVisitor.ContextItemType 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)
      • getIntegerBounds

        public IntegerValue[] getIntegerBounds()
        For an expression that returns an integer or a sequence of integers, get a lower and upper bound on the values of the integers that may be returned, from static analysis. The default implementation returns null, meaning "unknown" or "not applicable". Other implementations return an array of two IntegerValue objects, representing the lower and upper bounds respectively. The values UNBOUNDED_LOWER and UNBOUNDED_UPPER are used by convention to indicate that the value may be arbitrarily large. The values MAX_STRING_LENGTH and MAX_SEQUENCE_LENGTH are used to indicate values limited by the size of a string or the size of a sequence.
        Overrides:
        getIntegerBounds in class Expression
        Returns:
        the lower and upper bounds of integer values in the result, or null to indicate unknown or not applicable.
      • 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
      • 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:
        UserFunctionCall.NOT_TAIL_CALL if no tail call was found; UserFunctionCall.FOREIGN_TAIL_CALL if a tail call on a different function was found;
      • extendBindingList

        public 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
      • isVacuousExpression

        public boolean isVacuousExpression()
        Determine whether this is a vacuous expression as defined in the XQuery update specification
        Overrides:
        isVacuousExpression in class Expression
        Returns:
        true if this expression is vacuous
      • 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
      • iterate

        public SequenceIterator iterate​(XPathContext context)
                                 throws XPathException
        Iterate over the sequence of values
        Overrides:
        iterate in class Expression
        Parameters:
        context - supplies the context for evaluation
        Returns:
        a SequenceIterator that can be used to iterate over the result of the expression
        Throws:
        XPathException - if any dynamic error occurs evaluating the expression
      • 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 - if a dynamic error occurs
      • 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 - if evaluation fails
      • 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)
      • toString

        public java.lang.String toString()
        The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax
        Overrides:
        toString in class Expression
        Returns:
        a representation of the expression as a string
      • 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
      • explainSpecializedAttributes

        protected void explainSpecializedAttributes​(ExpressionPresenter out)