Class CopyModifyExpression

java.lang.Object
net.sf.saxon.expr.Expression
com.saxonica.ee.update.CopyModifyExpression
All Implemented Interfaces:
ExportAgent, Locatable, IdentityComparable, Traceable

public class CopyModifyExpression extends Expression
A copy-modify expression (called a "transform" expression in the XQuery Update specification)

Note that this expression doesn't actually perform the copy. It gets wrapped in a let expression that does let $var := $input.copy-of().

  • Constructor Details

    • CopyModifyExpression

      public CopyModifyExpression(Expression updateExp, Expression returnExp, int validationMode)
      Create a copy-modify expression (also known as a transform expresion)
      Parameters:
      updateExp - the expression appearing in the modify clause
      returnExp - the expression appearing in the return clause
      validationMode - the mode for validating the updated nodes (strict, lax, or skip)
  • Method Details

    • operands

      public Iterable<Operand> operands()
      Description copied from class: Expression
      Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.

      If the expression is a Callable, then it is required that the order of the operands returned by this function is the same as the order of arguments supplied to the corresponding call() method.

      Overrides:
      operands in class Expression
      Returns:
      an iterator containing the sub-expressions of this expression
    • getUpdateExp

      public Expression getUpdateExp()
    • setUpdateExp

      public void setUpdateExp(Expression updateExp)
    • getReturnExp

      public Expression getReturnExp()
    • setReturnExp

      public void setReturnExp(Expression returnExp)
    • getCopyBindings

      public Expression getCopyBindings()
    • setCopyBindings

      public void setCopyBindings(Expression copyBindings)
      Set the copy bindings. This is an expression whose value is the set of nodes that are allowed to be updated. Normally it will consist of a variable reference or a sequence of variable references.
      Parameters:
      copyBindings - the set of Let expressions that bind variables that were copied during the copy phase and that therefore may be updated during the modify phase
    • computeCardinality

      protected int computeCardinality()
      Determine the static cardinality of the expression. This establishes how many items there will be in the result of the expression, at compile time (i.e., without actually evaluating the result.
      Specified by:
      computeCardinality in class Expression
      Returns:
      one of the values Cardinality.ONE_OR_MORE, Cardinality.ZERO_OR_MORE, Cardinality.EXACTLY_ONE, Cardinality.ZERO_OR_ONE, Cardinality.EMPTY. This default implementation returns ZERO_OR_MORE (which effectively gives no information).
    • getItemType

      public ItemType getItemType()
      Determine the data type of the expression, if possible. All expression return sequences, in general; this method determines the type of the items within the sequence, assuming that (a) this is known in advance, and (b) it is the same for all items in the sequence.

      This method should always return a result, though it may be the best approximation that is available at the time.

      Specified by:
      getItemType in class Expression
      Returns:
      a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)
    • isUpdatingExpression

      public boolean isUpdatingExpression()
      Determine whether this is an updating expression as defined in the XQuery update specification
      Overrides:
      isUpdatingExpression in class Expression
      Returns:
      false: although this expression performs updates, it is not classified as an updating 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.
    • checkForUpdatingSubexpressions

      public void checkForUpdatingSubexpressions() throws XPathException
      Check to ensure that this expression does not contain any inappropriate updating subexpressions. This check is overridden for those expressions that permit updating subexpressions.
      Overrides:
      checkForUpdatingSubexpressions in class Expression
      Throws:
      XPathException - if the expression has a non-permitted updating subexpression
    • copy

      public Expression copy(RebindingMap rebindings)
      Copy an expression. This makes a deep copy.
      Specified by:
      copy in class Expression
      Parameters:
      rebindings - variables to be rebound
      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
    • export

      public void export(ExpressionPresenter out) 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:
      out - 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.
    • iterate

      public SequenceIterator iterate(XPathContext context) throws XPathException
      Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.
      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
    • 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
    • process

      public void process(Outputter output, XPathContext context) throws XPathException
      Process the instruction, without returning any tail calls
      Overrides:
      process in class Expression
      Parameters:
      output - the destination for the result
      context - The dynamic context, giving access to the current node,
      Throws:
      XPathException - if a dynamic error occurs
    • getElaborator

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