Package net.sf.saxon.expr

Class VariableReference

    • Constructor Detail

      • VariableReference

        public VariableReference​(StructuredQName name)
        Create a Variable Reference
        Parameters:
        name - the name of the variable

      • VariableReference

        public VariableReference​(Binding binding)
        Create a Variable Reference
        Parameters:
        binding - the variable binding to which this variable refers

    • Method Detail

      • setVariableName

        public void setVariableName​(StructuredQName name)
        Set the variable name
        Parameters:
        name - the name of the variable

      • getVariableName

        public StructuredQName getVariableName()
        Get the variable name
        Returns:
        the name of the variable

      • copy

        public abstract Expression copy​(RebindingMap rebindings)
        Create a clone copy of this VariableReference
        Specified by:
        copy in class Expression
        Parameters:
        rebindings - variables that need to switch to new bindings
        Returns:
        the cloned copy

      • getNetCost

        public int getNetCost()
        Description copied from class: Expression
        Return the net cost of evaluating this expression, excluding the cost of evaluating its operands. We take the cost of evaluating a simple scalar comparison or arithmetic expression as 1 (one).
        Overrides:
        getNetCost in class Expression
        Returns:
        the intrinsic cost of this operation, excluding the costs of evaluating the operands

      • setStaticType

        public void setStaticType​(SequenceType type,
                          GroundedValue value,
                          int properties)
        Set static type. This is a callback from the variable declaration object. As well as supplying the static type, it may also supply a compile-time value for the variable. As well as the type information, other static properties of the value are supplied: for example, whether the value is an ordered node-set.
        Specified by:
        setStaticType in interface BindingReference
        Parameters:
        type - the static type of the variable
        value - the value of the variable if this is a compile-time constant, or null otherwise
        properties - static properties of the expression to which the variable is bound

      • setFlattened

        public void setFlattened​(boolean flattened)
        Mark an expression as being "flattened". This is a collective term that includes extracting the string value or typed value, or operations such as simple value construction that concatenate text nodes before atomizing. The implication of all of these is that although the expression might return nodes, the identity of the nodes has no significance. This is called during type checking of the parent expression. At present, only variable references take any notice of this notification.
        Overrides:
        setFlattened in class Expression
        Parameters:
        flattened - set to true if the result of the expression is atomized or otherwise turned into an atomic value

      • isFlattened

        public boolean isFlattened()
        Test whether this variable reference is flattened - that is, whether it is atomized etc
        Returns:
        true if the value of the variable is atomized, or converted to a string or number

      • setFiltered

        public void setFiltered​(boolean filtered)
        Mark an expression as filtered: that is, it appears as the base expression in a filter expression. This notification currently has no effect except when the expression is a variable reference.
        Overrides:
        setFiltered in class Expression
        Parameters:
        filtered - if true, marks this expression as the base of a filter expression

      • isFiltered

        public boolean isFiltered()
        Determine whether this variable reference is filtered
        Returns:
        true if the value of the variable is filtered by a predicate

      • isInLoop

        public boolean isInLoop()
        Ask whether this variable reference appears in a loop relative to its declaration. By default, when in doubt, returns true. This is calculated during type-checking.
        Returns:
        true if this variable reference occurs in a loop, where the variable declaration is outside the loop

      • setInLoop

        public void setInLoop​(boolean inLoop)
        Say whether this variable reference appears in a loop relative to its declaration.
        Parameters:
        inLoop - true if this variable reference occurs in a loop, where the variable declaration is outside the loop

      • typeCheck

        public Expression typeCheck​(ExpressionVisitor visitor,
                            ContextItemStaticInfo contextInfo)
                     throws XPathException
        Type-check the expression. At this stage details of the static type must be known. If the variable has a compile-time value, this is substituted for the variable reference
        Overrides:
        typeCheck in class Expression
        Parameters:
        visitor - an expression visitor
        contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.
        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)

      • recomputeInLoop

        public void recomputeInLoop()

      • optimize

        public Expression optimize​(ExpressionVisitor visitor,
                           ContextItemStaticInfo contextItemType)
                    throws XPathException
        Optimize the expression. At this stage details of the static type must be known. If the variable has a compile-time value, this is substituted for the variable reference
        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)

      • fixup

        public void fixup​(Binding newBinding)
        Fix up this variable reference to a Binding object, which enables the value of the variable to be located at run-time.
        Specified by:
        fixup in interface BindingReference
        Parameters:
        newBinding - the Binding to which the variable refers

      • refineVariableType

        public void refineVariableType​(ItemType type,
                               int cardinality,
                               GroundedValue constantValue,
                               int properties)
        Provide additional information about the type of the variable, typically derived by analyzing the initializer of the variable binding
        Parameters:
        type - the item type of the variable
        cardinality - the cardinality of the variable
        constantValue - the actual value of the variable, if this is known statically, otherwise null
        properties - additional static properties of the variable's initializer

      • getItemType

        public ItemType getItemType()
        Determine the data type of the expression, if possible
        Specified by:
        getItemType in class Expression
        Returns:
        the type of the variable, if this can be determined statically; otherwise Type.ITEM (meaning not known in advance)

      • getStaticUType

        public UType getStaticUType​(UType contextItemType)
        Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.
        Overrides:
        getStaticUType in class Expression
        Parameters:
        contextItemType - the static context item type
        Returns:
        the static item type of the expression according to the XSLT 3.0 defined rules

      • 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.

      • supportsLazyEvaluation

        public boolean supportsLazyEvaluation()
        Ask whether the expression supports lazy evaluation.
        Overrides:
        supportsLazyEvaluation in class Expression
        Returns:
        false either if the expression cannot be evaluated lazily because it has dependencies that cannot be saved in the context, or because lazy evaluation is pointless (for example, for literals and variable references).

      • equals

        public boolean equals​(java.lang.Object other)
        Test if this expression is the same as another expression. (Note, we only compare expressions that have the same static and dynamic context).
        Overrides:
        equals in class Expression
        Parameters:
        other - the other operand; the result is false if this is not an Expression
        Returns:
        true if the other operand is an expression and if it can be determined that the two expressions are equivalent, in the sense that they will always return the same result.

      • computeHashCode

        protected int computeHashCode()
        get HashCode for comparing two expressions
        Overrides:
        computeHashCode in class Expression
        Returns:
        a computed hash code

      • getIntrinsicDependencies

        public int getIntrinsicDependencies()
        Description copied from class: Expression
        Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions. For example, position() has an intrinsic dependency on the context position, while (position()+1) does not. The default implementation of the method returns 0, indicating "no dependencies".
        Overrides:
        getIntrinsicDependencies in class Expression
        Returns:
        an integer containing bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty

      • getScopingExpression

        public Expression getScopingExpression()
        Get the innermost scoping expression of this expression, for expressions that directly depend on something in the dynamic context. For example, in the case of a local variable reference this is the expression that causes the relevant variable to be bound; for a context item expression it is the innermost focus-setting container. For expressions that have no intrinsic dependency on the dynamic context, the value returned is null; the scoping container for such an expression is the innermost scoping container of its operands.
        Overrides:
        getScopingExpression in class Expression
        Returns:
        the innermost scoping container of this expression

      • addToPathMap

        public PathMap.PathMapNodeSet addToPathMap​(PathMap pathMap,
                                           PathMap.PathMapNodeSet pathMapNodeSet)
        Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

        The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

        Overrides:
        addToPathMap in class Expression
        Parameters:
        pathMap - the PathMap to which the expression should be added
        pathMapNodeSet - the PathMapNodeSet to which the paths embodied in this expression should be added
        Returns:
        the pathMapNodeSet representing the points in the source document that are both reachable by this expression, and that represent possible results of this expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

      • evaluateItem

        public Item evaluateItem​(XPathContext c)
                  throws XPathException
        Description copied from class: Expression
        Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.
        Overrides:
        evaluateItem in class Expression
        Parameters:
        c - 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

      • process

        public void process​(Outputter output,
                    XPathContext c)
             throws XPathException
        Description copied from class: Expression
        Process the instruction
        Overrides:
        process in class Expression
        Parameters:
        output - the destination for the result
        c - The dynamic context, giving access to the current node, the current variables, etc.
        Throws:
        XPathException - if a dynamic error occurs

      • evaluateVariable

        public Sequence evaluateVariable​(XPathContext c)
                          throws XPathException
        Evaluate this variable
        Parameters:
        c - the XPath dynamic context
        Returns:
        the value of the variable
        Throws:
        XPathException - if any error occurs

      • getBinding

        public Binding getBinding()
        Get the object bound to the variable
        Returns:
        the Binding which declares this variable and associates it with a value

      • getDisplayName

        public java.lang.String getDisplayName()
        Get the display name of the variable. This is taken from the variable binding if possible
        Returns:
        the display name (a lexical QName

      • getEQName

        public java.lang.String getEQName()
        Get the EQName of the variable. This is taken from the variable binding if possible. The returned name is in the format Q{uri}local if in a namespace, or the local name alone if not.
        Returns:
        the EQName, or the local name if not in a namespace

      • 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

      • toShortString

        public java.lang.String toShortString()
        Produce a short string identifying the expression for use in error messages
        Overrides:
        toShortString in class Expression
        Returns:
        a short string, sufficient to identify the expression

      • 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 export() output displaying the expression.

      • export

        public void export​(ExpressionPresenter destination)
            throws XPathException
        Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
        Specified by:
        export in interface ExportAgent
        Specified by:
        export in class Expression
        Parameters:
        destination - the expression presenter used to display the structure
        Throws:
        XPathException - if the export fails, for example if an expression is found that won't work in the target environment.

      • getStreamerName

        public java.lang.String getStreamerName()
        Get the (partial) name of a class that supports streaming of this kind of expression
        Overrides:
        getStreamerName in class Expression
        Returns:
        the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class