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:

IdentityComparable

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

Field Summary

Fields

Modifier and Type	Field and Description
protected Pattern	p1
protected Pattern	p2

Fields inherited from class net.sf.saxon.expr.Expression

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD

Constructor Summary

Constructors

Constructor and Description
VennPattern(Pattern p1, Pattern p2) Constructor

Method Summary

Methods

Modifier and Type	Method and Description
int	allocateSlots(SlotManager slotManager, int nextFree) Allocate slots to any variables used within the pattern
void	bindCurrent(LocalBinding binding) Replace any calls on current() by a variable reference bound to the supplied binding
boolean	equals(Object other) Determine whether this pattern is the same as another pattern
void	export(ExpressionPresenter presenter) Diagnostic print of expression structure.
void	gatherComponentPatterns(Set<Pattern> set) Gather the component (non-Venn) patterns of this Venn pattern
int	getDependencies() Get the dependencies of the pattern.
Pattern	getLHS() Get the LHS of the union
protected abstract String	getOperatorName() Get the relevant operator: "union", "intersect", or "except"
Pattern	getRHS() Get the RHS of the union
int	hashCode() Hashcode supporting equals()
boolean	isMotionless(boolean allowExtensions) Test whether a pattern is motionless, that is, whether it can be evaluated against a node without repositioning the input stream.
Iterator<Expression>	iterateSubExpressions() Iterate over the subexpressions within this pattern
Iterable<Operand>	operands() Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.
void	promote(PromotionOffer offer, Expression parent) Offer promotion for subexpressions within this pattern.
void	setOriginalText(String pattern) Set the original text
Pattern	simplify() Simplify the pattern: perform any context-independent optimisations
String	toString() Get the original pattern text
Pattern	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) Type-check the pattern.

Methods inherited from class net.sf.saxon.pattern.Pattern

convertToTypedPattern, copy, effectiveBooleanValue, getDefaultPriority, getFingerprint, getHostLanguage, getItemType, getUType, make, matches, matchesBeneathAnchor, optimize, replaceCurrent, selectNodes, setPriority

Methods inherited from class net.sf.saxon.expr.PseudoExpression

computeCardinality, evaluateAsString, evaluateItem, getImplementationMethod, iterate, iterateEvents, process

Methods inherited from class net.sf.saxon.expr.Expression

addToPathMap, adoptChildExpression, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, clearStreamabilityData, computeDependencies, computeSpecialProperties, computeStaticProperties, doPromotion, dynamicError, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getConstructType, getCost, getEvaluationMethod, getExpressionCompiler, getExpressionName, getIntegerBounds, getIntrinsicDependencies, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getPosture, getPostureAndSweepIfKnown, getProperties, getProperty, getRetainedStaticContext, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStreamability, getStreamingAdjunct, getSweep, getSystemId, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isCallOnSystemFunction, isIdentical, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, makeStreamingAdjunct, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, optimizeForType, promote, promoteChildren, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setFiltered, setFlattened, setLocation, setParentExpression, setPostureAndSweep, setRetainedStaticContext, setRetainedStaticContextLocally, setStaticProperty, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, toShortString, toStreamingPattern, typeCheckChildren, typeError, unordered

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

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

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 - the parent expression

Throws:

XPathException - if any error is detected

setOriginalText

public void setOriginalText(String pattern)

Set the original text

Overrides:

setOriginalText in class Pattern

Parameters:

pattern - the original text of the pattern

isMotionless

public boolean isMotionless(boolean allowExtensions)

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

Parameters:

allowExtensions - true if Saxon extensions are allowed

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

iterateSubExpressions

public Iterator<Expression> 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

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

getOperatorName

protected abstract String getOperatorName()

Get the relevant operator: "union", "intersect", or "except"

Returns:

the operator, as a string

toString

public String toString()

Get the original pattern text

Overrides:

toString in class Pattern

Returns:

a representation of the expression as a string

export

public void export(ExpressionPresenter presenter)

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 class Pattern

Parameters:

presenter - the expression presenter used to display the structure