Package net.sf.saxon.pattern

Class 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".

    • Constructor Detail

      • VennPattern

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

    • Method Detail

      • operands

        public java.lang.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​(java.util.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​(java.lang.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 java.lang.String getOperatorName()
        Get the relevant operator: "union", "intersect", or "except"
        Returns:
        the operator, as a string

      • reconstruct

        public java.lang.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.