Package net.sf.saxon.expr

Class SuppliedParameterReference

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.SuppliedParameterReference
All Implemented Interfaces:
ExportAgent, Locatable, IdentityComparable, Traceable
public class SuppliedParameterReference extends Expression
Supplied parameter reference: this is an internal expression used to refer to the value of the n'th parameter supplied on a template call or a call to an inline function. It is used within a type-checking expression designed to check the consistency of the supplied value with the required type. This type checking is all done at run-time, because the binding of apply-templates to actual template rules is entirely dynamic.

  • Constructor Details

    • SuppliedParameterReference

      public SuppliedParameterReference(int slot)
      Constructor
      Parameters:
      slot - identifies this parameter. The value -1 indicates that the value is to be obtained from the dynamic stack held in the context object.

  • Method Details

    • getSlotNumber

      public int getSlotNumber()
      Get the slot number
      Returns:
      the slot number

    • setSuppliedType

      public void setSuppliedType(SequenceType type)
      Set the type of the supplied value if known
      Parameters:
      type - of the supplied value

    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
      Description copied from class: Expression
      Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.

      This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

      This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.

      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)

    • optimize

      public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) throws XPathException
      Description copied from class: Expression
      Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.

      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.

      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)

    • getItemType

      public ItemType getItemType()
      Determine the data type of the expression, if possible.
      Specified by:
      getItemType in class Expression
      Returns:
      Type.ITEM, because we don't know the type of the supplied value in advance.

    • getIntrinsicDependencies

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

    • computeCardinality

      protected int computeCardinality()
      Get the static cardinality
      Specified by:
      computeCardinality in class Expression
      Returns:
      ZERO_OR_MORE, unless we know the type of the supplied value in advance.

    • 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).

    • copy

      public Expression copy(RebindingMap rebindings)
      Copy an expression. This makes a deep copy.
      Specified by:
      copy in class Expression
      Parameters:
      rebindings - variables that need to be re-bound
      Returns:
      the copy of the original expression

    • 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 directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.
      Specified by:
      getImplementationMethod in class Expression
      Returns:
      the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

    • evaluateVariable

      public Sequence evaluateVariable(XPathContext c)
      Get the value of this expression in a given context.
      Parameters:
      c - the XPathContext which contains the relevant variable bindings
      Returns:
      the value of the variable, if it is defined

    • iterate

      public SequenceIterator iterate(XPathContext context) throws XPathException
      Get the value of this expression in a given context.
      Overrides:
      iterate in class Expression
      Parameters:
      context - 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 context) throws XPathException
      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:
      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

    • getExpressionName

      public 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.

    • toString

      public 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

    • getElaborator

      public Elaborator getElaborator()
      Description copied from class: Expression
      Make an elaborator for this expression
      Overrides:
      getElaborator in class Expression
      Returns:
      an appropriate Elaborator