Package net.sf.saxon.pattern

Class VennPattern

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.PseudoExpression
net.sf.saxon.pattern.Pattern
net.sf.saxon.pattern.VennPattern
All Implemented Interfaces:
ExportAgent, Locatable, IdentityComparable, Traceable
Direct Known Subclasses:
ExceptPattern, IntersectPattern, UnionPattern
public abstract class VennPattern extends Pattern
Abstract pattern formed as the union, intersection, or difference of two other patterns; concrete subclasses are used for the different operators. Bug #5368 concludes that we can't simply treat "A except B" as meaning that a node must match pattern A and not match pattern B; similarly for the intersect operator. There are however special cases where we can do so, for example "@* except @code".

  • Field Details

  • Constructor Details

    • VennPattern

      public VennPattern(Pattern p1, Pattern p2)
      Constructor
      Parameters:
      p1 - the left-hand operand
      p2 - the right-hand operand

  • Method Details

    • operands

      public Iterable<Operand> operands()
      Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression. Default implementation works off the results of iterateSubExpressions()

      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

    • simplify

      public Pattern simplify() throws XPathException
      Simplify the pattern: perform any context-independent optimisations
      Overrides:
      simplify in class Pattern
      Returns:
      the simplified expression (or the original if unchanged, or if modified in-situ)
      Throws:
      XPathException - if an error is discovered during expression rewriting

    • typeCheck

      public Pattern typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) throws XPathException
      Type-check the pattern. This is only needed for patterns that contain variable references or function calls.
      Overrides:
      typeCheck in class Pattern
      Parameters:
      visitor - the expression visitor
      contextItemType - the type of the context item at the point where the pattern is defined. Set to null if it is known that the context item is undefined.
      Returns:
      the optimised Pattern
      Throws:
      XPathException - if an error is discovered during this phase (typically a type error)

    • bindCurrent

      public void bindCurrent(LocalBinding binding)
      Replace any calls on current() by a variable reference bound to the supplied binding
      Overrides:
      bindCurrent in class Pattern

    • isMotionless

      public boolean isMotionless()
      Test whether a pattern is motionless, that is, whether it can be evaluated against a node without repositioning the input stream. This is a necessary condition for patterns used as the match pattern of a streamed template rule.
      Overrides:
      isMotionless in class Pattern
      Returns:
      true if the pattern is motionless, that is, if it can be evaluated against a streamed node without changing the position in the streamed input file

    • allocateSlots

      public int allocateSlots(SlotManager slotManager, int nextFree)
      Allocate slots to any variables used within the pattern
      Overrides:
      allocateSlots in class Pattern
      Parameters:
      slotManager - represents the stack frame on which slots are allocated
      nextFree - the next slot that is free to be allocated @return the next slot that is free to be allocated
      Returns:
      the next slot that is free to be allocated

    • gatherComponentPatterns

      public void gatherComponentPatterns(Set<Pattern> set)
      Gather the component (non-Venn) patterns of this Venn pattern
      Parameters:
      set - the set into which the components will be added

    • getDependencies

      public int getDependencies()
      Get the dependencies of the pattern. The only possible dependency for a pattern is on local variables. This is analyzed in those patterns where local variables may appear.
      Overrides:
      getDependencies in class Pattern
      Returns:
      the dependencies, as a bit-significant mask

    • getLHS

      public Pattern getLHS()
      Get the LHS of the union
      Returns:
      the first operand of the union

    • getRHS

      public Pattern getRHS()
      Get the RHS of the union
      Returns:
      the second operand of the union

    • matchesCurrentGroup

      public boolean matchesCurrentGroup()
      Ask whether the pattern is anchored on a call on current-group()
      Overrides:
      matchesCurrentGroup in class Pattern
      Returns:
      true if calls on matchesBeneathAnchor should test with all nodes in the current group as anchor nodes. If false, only the first node in a group is treated as the anchor node

    • equals

      public boolean equals(Object other)
      Determine whether this pattern is the same as another pattern
      Overrides:
      equals in class Expression
      Parameters:
      other - the other object
      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()
      Hashcode supporting equals()
      Overrides:
      computeHashCode in class Expression
      Returns:
      a computed hash code

    • getOperatorName

      protected abstract String getOperatorName()
      Get the relevant operator: "union", "intersect", or "except"
      Returns:
      the operator, as a string

    • reconstruct

      public String reconstruct()
      Get the original pattern text
      Overrides:
      reconstruct in class Pattern

    • export

      public void export(ExpressionPresenter presenter) throws XPathException
      Description copied from class: Expression
      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 Pattern
      Parameters:
      presenter - 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.