net.sf.saxon.pattern
Class VennPattern

java.lang.Object
  extended by net.sf.saxon.pattern.Pattern
      extended by net.sf.saxon.pattern.VennPattern
All Implemented Interfaces:
Serializable, SourceLocator, Container, PatternFinder
Direct Known Subclasses:
ExceptPattern, IntersectPattern, UnionPattern

public abstract class VennPattern
extends Pattern

A pattern formed as the union, intersection, or difference of two other patterns

See Also:
Serialized Form

Field Summary
protected  Pattern p1
           
protected  Pattern p2
           
 
Constructor Summary
VennPattern(Pattern p1, Pattern p2)
          Constructor
 
Method Summary
 int allocateSlots(StaticContext env, SlotManager slotManager, int nextFree)
          Allocate slots to any variables used within the pattern
 Pattern analyze(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)
          Type-check the pattern.
 boolean equals(Object other)
          Determine whether this pattern is the same as another pattern
 void gatherComponentPatterns(Set set)
          Gather the component (non-Venn) patterns of this Venn pattern
 int getDependencies()
          Get the dependencies of the pattern.
 ItemType getItemType()
          Get an ItemType that all the items matching this pattern must satisfy
 Pattern getLHS()
          Get the LHS of the union
 int getNodeKind()
          Determine the types of nodes to which this pattern applies.
 Pattern getRHS()
          Get the RHS of the union
 int hashCode()
          Hashcode supporting equals()
 Iterator iterateSubExpressions()
          Iterate over the subexpressions within this pattern
 void promote(PromotionOffer offer, Expression parent)
          Offer promotion for subexpressions within this pattern.
 boolean replaceSubExpression(Expression original, Expression replacement)
          Replace a subexpression by a replacement subexpression
 void resolveCurrent(LetExpression let, PromotionOffer offer, boolean topLevel)
          If the pattern contains any calls on current(), this method is called to modify such calls to become variable references to a variable declared in a specially-allocated local variable
 void setExecutable(Executable executable)
          Set the executable containing this pattern
 void setLineNumber(int lineNumber)
          Override method to set the system ID, so it's set on both halves
 void setOriginalText(String pattern)
          Set the original text
 void setSystemId(String systemId)
          Override method to set the system ID, so it's set on both halves
 Pattern simplify(ExpressionVisitor visitor)
          Simplify the pattern: perform any context-independent optimisations
 
Methods inherited from class net.sf.saxon.pattern.Pattern
getColumnNumber, getContainerGranularity, getDefaultPriority, getExecutable, getFingerprint, getHostLanguage, getLineNumber, getLocationProvider, getPublicId, getSystemId, internalMatches, make, matches, matchesBeneathAnchor, selectNodes, toString
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Field Detail

p1

protected Pattern p1

p2

protected Pattern p2
Constructor Detail

VennPattern

public VennPattern(Pattern p1,
                   Pattern p2)
Constructor

Parameters:
p1 - the left-hand operand
p2 - the right-hand operand
Method Detail

setExecutable

public void setExecutable(Executable executable)
Set the executable containing this pattern

Overrides:
setExecutable in class Pattern
Parameters:
executable - the executable

simplify

public Pattern simplify(ExpressionVisitor visitor)
                 throws XPathException
Simplify the pattern: perform any context-independent optimisations

Overrides:
simplify in class Pattern
Parameters:
visitor - an expression visitor
Returns:
the optimised Pattern
Throws:
XPathException

analyze

public Pattern analyze(ExpressionVisitor visitor,
                       ExpressionVisitor.ContextItemType contextItemType)
                throws XPathException
Type-check the pattern. This is only needed for patterns that contain variable references or function calls.

Overrides:
analyze 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

resolveCurrent

public void resolveCurrent(LetExpression let,
                           PromotionOffer offer,
                           boolean topLevel)
                    throws XPathException
If the pattern contains any calls on current(), this method is called to modify such calls to become variable references to a variable declared in a specially-allocated local variable

Overrides:
resolveCurrent in class Pattern
Parameters:
let - the expression that assigns the local variable. This returns a dummy result, and is executed just before evaluating the pattern, to get the value of the context item into the variable.
offer - A PromotionOffer used to process the expressions and change the call on current() into a variable reference
topLevel -
Throws:
XPathException

promote

public void promote(PromotionOffer offer,
                    Expression parent)
             throws XPathException
Offer promotion for subexpressions within this pattern. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. By default the offer is not accepted - this is appropriate in the case of simple expressions such as constant values and variable references where promotion would give no performance advantage. This method is always called at compile time.

Unlike the corresponding method on Expression, this method does not return anything: it can make internal changes to the pattern, but cannot return a different pattern. Only certain kinds of promotion are applicable within a pattern: specifically, promotions affecting local variable references within the pattern.

Overrides:
promote in class Pattern
Parameters:
offer - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression
parent -
Throws:
XPathException - if any error is detected

replaceSubExpression

public boolean replaceSubExpression(Expression original,
                                    Expression replacement)
Replace a subexpression by a replacement subexpression

Overrides:
replaceSubExpression in class Pattern
Parameters:
original - the expression to be replaced
replacement - the new expression to be inserted in its place
Returns:
true if the replacement was carried out

setOriginalText

public void setOriginalText(String pattern)
Set the original text

Overrides:
setOriginalText in class Pattern
Parameters:
pattern - the original text of the pattern

allocateSlots

public int allocateSlots(StaticContext env,
                         SlotManager slotManager,
                         int nextFree)
Allocate slots to any variables used within the pattern

Overrides:
allocateSlots in class Pattern
Parameters:
env - the static context in the XSLT stylesheet
slotManager -
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 set)
Gather the component (non-Venn) patterns of this Venn pattern

Parameters:
set - the set into which the components will be added

getNodeKind

public int getNodeKind()
Determine the types of nodes to which this pattern applies. Used for optimisation. For patterns that match nodes of several types, return Node.NODE

Overrides:
getNodeKind in class Pattern
Returns:
the type of node matched by this pattern. e.g. Node.ELEMENT or Node.TEXT

getItemType

public ItemType getItemType()
Get an ItemType that all the items matching this pattern must satisfy

Specified by:
getItemType in class Pattern
Returns:
an ItemType, as specific as possible, which all the matching items satisfy

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

iterateSubExpressions

public Iterator iterateSubExpressions()
Iterate over the subexpressions within this pattern

Overrides:
iterateSubExpressions in class Pattern
Returns:
an iterator over the subexpressions.

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

setSystemId

public void setSystemId(String systemId)
Override method to set the system ID, so it's set on both halves

Overrides:
setSystemId in class Pattern
Parameters:
systemId - the URI of the module containing the pattern

setLineNumber

public void setLineNumber(int lineNumber)
Override method to set the system ID, so it's set on both halves

Overrides:
setLineNumber in class Pattern
Parameters:
lineNumber - the line number of the pattern in the source module

equals

public boolean equals(Object other)
Determine whether this pattern is the same as another pattern

Overrides:
equals in class Object
Parameters:
other - the other object

hashCode

public int hashCode()
Hashcode supporting equals()

Overrides:
hashCode in class Object


Copyright (c) 2004-2011 Saxonica Limited. All rights reserved.