Package net.sf.saxon.expr

Class VennExpression

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.BinaryExpression
net.sf.saxon.expr.VennExpression
All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, Locator
public class VennExpression extends BinaryExpression
An expression representing a nodeset that is a union, difference, or intersection of two other NodeSets
See Also:

  • Constructor Details

    • VennExpression

      public VennExpression(Expression p1, int op, Expression p2)
      Constructor
      Parameters:
      p1 - the left-hand operand
      op - the operator (union, intersection, or difference)
      p2 - the right-hand operand

  • Method Details

    • getItemType

      public final ItemType getItemType(TypeHierarchy th)
      Determine the data type of the items returned by this expression
      Specified by:
      getItemType in class Expression
      Parameters:
      th - the type hierarchy cache
      Returns:
      the data type

    • computeCardinality

      public final int computeCardinality()
      Determine the static cardinality of the expression
      Overrides:
      computeCardinality in class BinaryExpression
      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

    • computeSpecialProperties

      public int computeSpecialProperties()
      Get the static properties of this expression (other than its type). The result is bit-signficant. 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 BinaryExpression
      Returns:
      StaticProperty.NON_CREATIVE. This is overridden for some subclasses.

    • gatherComponents

      public void gatherComponents(int operator, Set set)
      Gather the component operands of a union or intersect expression
      Parameters:
      operator - union or intersect
      set - the set into which the components are to be gathered. If the operator is union, this follows the tree gathering all operands of union expressions. Ditto, mutatis mutandis, for intersect expressions.

    • simplify

      public Expression simplify(ExpressionVisitor visitor) throws XPathException
      Simplify the expression
      Overrides:
      simplify in class BinaryExpression
      Parameters:
      visitor - an expression visitor
      Returns:
      the simplified expression
      Throws:
      XPathException - if an error is discovered during expression rewriting

    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
      Type-check the expression
      Overrides:
      typeCheck in class BinaryExpression
      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 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, 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 BinaryExpression
      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)

    • copy

      public Expression copy()
      Copy an expression. This makes a deep copy.
      Specified by:
      copy in class Expression
      Returns:
      the copy of the original expression

    • equals

      public boolean equals(Object other)
      Is this expression the same as another expression?
      Overrides:
      equals in class BinaryExpression

    • hashCode

      public int hashCode()
      Description copied from class: BinaryExpression
      Get a hashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.
      Overrides:
      hashCode in class BinaryExpression

    • iterate

      public SequenceIterator iterate(XPathContext c) throws XPathException
      Iterate over the value of the expression. The result will always be sorted in document order, with duplicates eliminated
      Specified by:
      iterate in interface SequenceIterable
      Overrides:
      iterate in class Expression
      Parameters:
      c - The context for evaluation
      Returns:
      a SequenceIterator representing the union of the two operands
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression

    • effectiveBooleanValue

      public boolean effectiveBooleanValue(XPathContext context) throws XPathException
      Get the effective boolean value. In the case of a union expression, this is reduced to an OR expression, for efficiency
      Overrides:
      effectiveBooleanValue in class Expression
      Parameters:
      context - The context in which the expression is to be evaluated
      Returns:
      the effective boolean value
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression