Class VennExpression

All Implemented Interfaces:
ExportAgent, Locatable, IdentityComparable, Traceable
Direct Known Subclasses:
SingletonIntersectExpression

public class VennExpression extends BinaryExpression
An expression representing a nodeset that is a union, difference, or intersection of two other NodeSets
  • 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

    • simplify

      public Expression simplify() throws XPathException
      Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation simplifies its operands.
      Overrides:
      simplify in class Expression
      Returns:
      the simplified expression (or the original if unchanged, or if modified in-situ)
      Throws:
      XPathException - if an error is discovered during expression rewriting
    • 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 explain() output displaying the expression.
    • getItemType

      public final ItemType getItemType()
      Determine the data type of the items returned by this expression
      Specified by:
      getItemType in class Expression
      Returns:
      the data type
    • getStaticUType

      public UType getStaticUType(UType contextItemType)
      Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.
      Overrides:
      getStaticUType in class Expression
      Parameters:
      contextItemType - the static type of the context item
      Returns:
      the static item type of the expression according to the XSLT 3.0 defined rules
    • computeCardinality

      protected 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. May also return StaticProperty.ALLOWS_ZERO if the result is known to be an empty sequence, or StaticProperty.ALLOWS_MANY if if is known to return a sequence of length two or more.
    • computeSpecialProperties

      protected 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.NO_NODES_NEWLY_CREATED. This is overridden for some subclasses.
    • gatherComponents

      public void gatherComponents(int operator, Set<Expression> 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.
    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
      Type-check the expression
      Overrides:
      typeCheck in class BinaryExpression
      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
      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)
    • unordered

      public Expression unordered(boolean retainAllNodes, boolean forStreaming)
      Replace this expression by an expression that returns the same result but without regard to order
      Overrides:
      unordered in class Expression
      Parameters:
      retainAllNodes - true if all nodes in the result must be retained; false if duplicates can be eliminated
      forStreaming - set to true if optimizing for streaming
      Returns:
      an expression that delivers the same nodes in a more convenient order
    • 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 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.
      Overrides:
      getImplementationMethod in class BinaryExpression
      Returns:
      the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD
    • getOperandRole

      protected OperandRole getOperandRole(int arg)
      Get the operand role (applies to both operands)
      Overrides:
      getOperandRole in class BinaryExpression
      Parameters:
      arg - which argument: 0 for the lhs, 1 for the rhs
      Returns:
      the operand role
    • equals

      public boolean equals(Object other)
      Is this expression the same as another expression?
      Overrides:
      equals in class BinaryExpression
      Parameters:
      other - the other operand; the result is false if this is not an Expression
      Returns:
      true if the other operand is an expression and if it can be determined that the two expressions are equivalent, in the sense that they will always return the same result.
    • computeHashCode

      protected int computeHashCode()
      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:
      computeHashCode in class BinaryExpression
      Returns:
      a computed hash code
    • toPattern

      public Pattern toPattern(Configuration config) throws XPathException
      Convert this expression to an equivalent XSLT pattern
      Overrides:
      toPattern in class Expression
      Parameters:
      config - the Saxon configuration
      Returns:
      the equivalent pattern
      Throws:
      XPathException - if conversion is not possible
    • tag

      protected String tag()
      Get the element name used to identify this expression in exported expression format
      Overrides:
      tag in class BinaryExpression
      Returns:
      the element name used to identify this expression
    • 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
      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
    • getStreamerName

      public String getStreamerName()
      Get the (partial) name of a class that supports streaming of this kind of expression
      Overrides:
      getStreamerName in class Expression
      Returns:
      the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class
    • getElaborator

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