Class VariableReference

java.lang.Object
net.sf.saxon.expr.ComputedExpression
net.sf.saxon.expr.VariableReference
All Implemented Interfaces:
Serializable, SourceLocator, BindingReference, Container, Expression, InstructionInfoProvider
Direct Known Subclasses:
LocalVariableReference

public class VariableReference extends ComputedExpression implements BindingReference
Variable reference: a reference to a variable. This may be an XSLT-defined variable, a range variable defined within the XPath expression, or a variable defined in some other static context.
See Also:
  • Field Details

  • Constructor Details

    • VariableReference

      public VariableReference()
    • VariableReference

      public VariableReference(VariableDeclaration declaration)
      Constructor
      Parameters:
      declaration - the variable declaration to which this variable refers
  • Method Details

    • copy

      public VariableReference copy()
      Create a clone copy of this VariableReference
    • setStaticType

      public void setStaticType(SequenceType type, Value 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
    • typeCheck

      public Expression typeCheck(StaticContext env, ItemType contextItemType) 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
      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:
      XPathException
    • optimize

      public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType) 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
      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:
      XPathException
    • fixup

      public void fixup(Binding binding)
      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
    • refineVariableReference

      public void refineVariableReference()
      Replace this VariableReference where appropriate by a more efficient implementation. This can only be done after all slot numbers are allocated. The efficiency is gained by binding the VariableReference directly to a local or global slot, rather than going via the Binding object
    • getItemType

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

      public int computeCardinality()
      Get the static cardinality
      Specified by:
      computeCardinality in class ComputedExpression
    • computeSpecialProperties

      public int computeSpecialProperties()
      Determine the special properties of this expression
      Overrides:
      computeSpecialProperties in class ComputedExpression
      Returns:
      StaticProperty.NON_CREATIVE (unless the variable is assignable using saxon:assign)
    • equals

      public boolean equals(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 Object
    • hashCode

      public int hashCode()
      get HashCode for comparing two expressions
      Overrides:
      hashCode in class Object
    • getIntrinsicDependencies

      public int getIntrinsicDependencies()
      Description copied from class: ComputedExpression
      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 ComputedExpression
      Returns:
      a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty
    • promote

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

      public int getImplementationMethod()
      An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided. This implementation provides both all three methods natively.
      Specified by:
      getImplementationMethod in interface Expression
      Overrides:
      getImplementationMethod in class ComputedExpression
    • iterate

      public SequenceIterator iterate(XPathContext c) throws XPathException
      Get the value of this variable in a given context.
      Specified by:
      iterate in interface Expression
      Overrides:
      iterate in class ComputedExpression
      Parameters:
      c - the XPathContext which contains the relevant variable bindings
      Returns:
      the value of the variable, if it is defined
      Throws:
      XPathException - if the variable is undefined
    • evaluateItem

      public Item evaluateItem(XPathContext c) throws XPathException
      Description copied from class: ComputedExpression
      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.
      Specified by:
      evaluateItem in interface Expression
      Overrides:
      evaluateItem in class ComputedExpression
      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(XPathContext c) throws XPathException
      Description copied from class: ComputedExpression
      Process the instruction, without returning any tail calls
      Specified by:
      process in interface Expression
      Overrides:
      process in class ComputedExpression
      Parameters:
      c - The dynamic context, giving access to the current node, the current variables, etc.
      Throws:
      XPathException
    • evaluateVariable

      public ValueRepresentation evaluateVariable(XPathContext c) throws XPathException
      Throws:
      XPathException
    • getBinding

      public Binding getBinding()
      Get the object bound to the variable
    • display

      public void display(int level, 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
      config -