net.sf.saxon.expr

Class VennExpression

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.BinaryExpression

net.sf.saxon.expr.VennExpression

All Implemented Interfaces:

Serializable, SourceLocator, LocationProvider, SaxonLocator, InstructionInfo, Locator

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

See Also:

Serialized Form

Field Summary

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

operand0, operand1, operator

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

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, INHERITED_CONTEXT, INSPECTION_CONTEXT, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, NAVIGATION_CONTEXT, NODE_VALUE_CONTEXT, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, W3C_CONSUMING, W3C_FREE_RANGING, W3C_GROUP_CONSUMING, W3C_MOTIONLESS, WATCH_METHOD

Constructor Summary

Constructors

Constructor and Description
VennExpression(Expression p1, int op, Expression p2) Constructor

Method Summary

Methods

Modifier and Type	Method and Description
int	computeCardinality() Determine the static cardinality of the expression
int	computeSpecialProperties() Get the static properties of this expression (other than its type).
Expression	copy() Copy an expression.
boolean	effectiveBooleanValue(XPathContext context) Get the effective boolean value.
boolean	equals(Object other) Is this expression the same as another expression?
void	gatherComponents(int operator, Set set) Gather the component operands of a union or intersect expression
ExpressionCompiler	getExpressionCompiler() Return the compiler of the Venn expression
String	getExpressionName() Get a name identifying the kind of expression, in terms meaningful to a user.
ItemType	getItemType(TypeHierarchy th) Determine the data type of the items returned by this expression
int	getStreamability(int syntacticContext, boolean allowExtensions, List<String> reasons) Get the "sweep" of this expression as defined in the W3C streamability specifications.
int	hashCode() Get a hashCode for comparing two expressions.
SequenceIterator	iterate(XPathContext c) Iterate over the value of the expression.
Iterator<SubExpressionInfo>	iterateSubExpressionInfo() Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.
Expression	optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Perform optimisation of an expression and its subexpressions.
Expression	promote(PromotionOffer offer, Expression parent) Promote this expression if possible
Expression	simplify(ExpressionVisitor visitor) Simplify the expression
Pattern	toPattern(Configuration config, boolean is30) Convert this expression to an equivalent XSLT pattern
Pattern	toStreamingPattern(Configuration config, List<String> reasonForFailure) Convert this expression to a streaming pattern (a pattern used internally to match nodes during push processing of an event stream)
Expression	typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Type-check the expression

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

displayOperator, explain, explainExtraAttributes, getArguments, getOperands, getOperator, isAssociative, isCommutative, isInverse, iterateSubExpressions, replaceSubExpression, setFlattened, toString

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

addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getImplementationMethod, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getStreamingAdjunct, getSystemId, getSystemId, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setLocationId, staticTypeCheck, suppressValidation, typeError

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

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 Detail

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(TypeHierarchy th)

Determine the data type of the items returned by this expression

Specified by:

getItemType in class Expression

Parameters:

th - the type hierarchy cache

Returns:

the data type

computeCardinality

public 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

computeSpecialProperties

public 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.NON_CREATIVE. This is overridden for some subclasses.

gatherComponents

public void gatherComponents(int operator,
                    Set 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.

simplify

public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException

Simplify the expression

Overrides:

simplify in class BinaryExpression

Parameters:

visitor - an expression visitor

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                   ExpressionVisitor.ContextItemType contextItemType)
                     throws XPathException

Type-check the expression

Overrides:

typeCheck 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 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,
                  ExpressionVisitor.ContextItemType 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)

promote

public Expression promote(PromotionOffer offer,
                 Expression parent)
                   throws XPathException

Promote this expression if possible

Overrides:

promote in class BinaryExpression

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 containing expression in the expression tree

Returns:

if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression

Throws:

XPathException - if any error is detected

copy

public Expression copy()

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Returns:

the copy of the original expression

iterateSubExpressionInfo

public Iterator<SubExpressionInfo> iterateSubExpressionInfo()

Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.

Overrides:

iterateSubExpressionInfo in class BinaryExpression

Returns:

an iterator containing the sub-expressions of this expression

equals

public boolean equals(Object other)

Is this expression the same as another expression?

Overrides:

equals in class BinaryExpression

hashCode

public int hashCode()

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:

hashCode in class BinaryExpression

toPattern

public Pattern toPattern(Configuration config,
                boolean is30)
                  throws XPathException

Convert this expression to an equivalent XSLT pattern

Overrides:

toPattern in class Expression

Parameters:

config - the Saxon configuration

is30 - true if this is XSLT 3.0

Returns:

the equivalent pattern

Throws:

XPathException - if conversion is not possible

toStreamingPattern

public Pattern toStreamingPattern(Configuration config,
                         List<String> reasonForFailure)

Convert this expression to a streaming pattern (a pattern used internally to match nodes during push processing of an event stream)

Overrides:

toStreamingPattern in class Expression

Parameters:

config - the Saxon configuration

reasonForFailure - a list which will be populated with messages giving reasons why the expression cannot be converted

Returns:

the equivalent pattern if conversion succeeds; otherwise null

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

getStreamability

public int getStreamability(int syntacticContext,
                   boolean allowExtensions,
                   List<String> reasons)

Get the "sweep" of this expression as defined in the W3C streamability specifications. This provides an assessment of stylesheet code against the W3C criteria for guaranteed streamability, and is implemented to allow these criteria to be tested. It is not the case that all expression that emerge as streamable from this analysis are currently capable of being streamed by Saxon

Overrides:

getStreamability in class Expression

Parameters:

syntacticContext - one of the values Expression.NAVIGATION_CONTEXT, Expression.NODE_VALUE_CONTEXT, Expression.INHERITED_CONTEXT, Expression.INSPECTION_CONTEXT

allowExtensions - if false, the definition of "guaranteed streamability" in the W3C specification is used. If true, Saxon extensions are permitted, which make some

reasons - the caller may supply a list, in which case the implementation may add to this list a message explaining why the construct is not streamable, suitable for inclusion in an error message.

Returns:

one of the values Expression.W3C_MOTIONLESS, Expression.W3C_CONSUMING, Expression.W3C_GROUP_CONSUMING, Expression.W3C_FREE_RANGING

getExpressionCompiler

public ExpressionCompiler getExpressionCompiler()

Return the compiler of the Venn expression

Overrides:

getExpressionCompiler in class Expression

Returns:

the relevant ExpressionCompiler