Class Subsequence

All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, Locator

public class Subsequence extends SystemFunction
Implements the XPath 2.0 subsequence() function
See Also:
  • Constructor Details

    • Subsequence

      public Subsequence()
  • Method Details

    • getItemType

      public ItemType getItemType(TypeHierarchy th)
      Determine the data type of the items in the sequence
      Overrides:
      getItemType in class SystemFunction
      Parameters:
      th - the type hierarchy cache
      Returns:
      the type of the argument
    • computeSpecialProperties

      public int computeSpecialProperties()
      Get the static properties of this expression (other than its type). The result is bit-significant. 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 SystemFunction
      Returns:
      the special properties, as a bit-significant integer
    • computeCardinality

      public int computeCardinality()
      Determine the cardinality of the function.
      Overrides:
      computeCardinality in class SystemFunction
      Returns:
      the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE
    • optimize

      public Expression optimize(ExpressionVisitor visitor, 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.

      Overrides:
      optimize in class SystemFunction
      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)
    • iterate

      public SequenceIterator iterate(XPathContext context) throws XPathException
      Evaluate the function to return an iteration of selected nodes.
      Specified by:
      iterate in interface SequenceIterable
      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