Class LetExpression

    • Field Detail

      • refCount

        int refCount
      • evaluationMode

        int evaluationMode
    • Constructor Detail

      • LetExpression

        public LetExpression()
    • Method Detail

      • setIndexedVariable

        public void setIndexedVariable()
      • typeCheck

        public Expression typeCheck​(StaticContext env,
                                    ItemType contextItemType)
                             throws XPathException
        Type-check the expression
        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 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
      • 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.
        Specified by:
        checkPermittedContents in interface Expression
        Overrides:
        checkPermittedContents in class ComputedExpression
        Parameters:
        parentType - The schema type
        env - the static context
        whole - true if this expression is expected to make the whole content of the type, false if it is expected to make up only a part
        Throws:
        XPathException - if the expression doesn't match the required content type
      • evaluateItem

        public Item evaluateItem​(XPathContext context)
                          throws XPathException
        Evaluate the expression as a singleton
        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
      • getItemType

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

        public int computeSpecialProperties()
        Get the static properties of this expression (other than its type). The result is bit-signficant. 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 ComputedExpression
      • markTailFunctionCalls

        public boolean markTailFunctionCalls​(int nameCode,
                                             int arity)
        Mark tail function calls
        Overrides:
        markTailFunctionCalls in class ComputedExpression
        Returns:
        true if a tail recursive call was found and if this call accounts for the whole of the value.
      • promote

        public Expression promote​(PromotionOffer offer)
                           throws XPathException
        Promote this expression if possible
        Specified by:
        promote in interface Expression
        Overrides:
        promote in class Assignation
        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
      • processLeavingTail

        public TailCall processLeavingTail​(XPathContext context)
                                    throws XPathException
        ProcessLeavingTail: called to do the real work of this instruction. The results of the instruction are written to the current Receiver, which can be obtained via the Controller.
        Specified by:
        processLeavingTail in interface TailCallReturner
        Parameters:
        context - The dynamic context of the transformation, giving access to the current node, the current variables, etc.
        Returns:
        null if the instruction has completed execution; or a TailCall indicating a function call or template call that is delegated to the caller, to be made after the stack has been unwound so as to save stack space.
        Throws:
        XPathException
      • display

        public void display​(int level,
                            java.io.PrintStream out,
                            Configuration config)
        Diagnostic print of expression structure
        Specified by:
        display in interface Expression
        Parameters:
        level - indentation level for this expression
        out - Output destination