Package net.sf.saxon.expr

Class SingletonIntersectExpression

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.BinaryExpression

net.sf.saxon.expr.VennExpression

net.sf.saxon.expr.SingletonIntersectExpression

All Implemented Interfaces:

ExportAgent, Locatable, IdentityComparable, Traceable

public class SingletonIntersectExpression
extends VennExpression

This expression is equivalent to (A intersect B) in the case where A has cardinality zero-or-one. This is handled as a special case because the standard sort-merge algorithm involves an unnecessary sort on B.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	SingletonIntersectExpression.SingletonIntersectElaborator	Elaborator for a Venn expression: that is A union B, A intersect B, or A except B

Nested classes/interfaces inherited from class net.sf.saxon.expr.VennExpression

VennExpression.VennElaborator

Field Summary

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

operator

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

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

Constructor Summary

Constructors

Constructor	Description
SingletonIntersectExpression(Expression p1, int op, Expression p2)	Special case of an intersect expression where the first argument is a singleton

Method Summary

Modifier and Type	Method	Description
static boolean	containsNode(SequenceIterator iter, NodeInfo m)	Ask whether the sequence supplied in the first argument contains the node supplied in the second
Expression	copy(RebindingMap rebindings)	Copy an expression.
protected java.lang.String	displayOperator()	Display the operator used by this binary expression
boolean	effectiveBooleanValue(XPathContext c)	Get the effective boolean value.
Elaborator	getElaborator()	Make an elaborator for this expression
java.lang.String	getExpressionName()	Get a name identifying the kind of expression, in terms meaningful to a user.
SequenceIterator	iterate(XPathContext c)	Iterate over the value of the expression.
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType)	Perform optimisation of an expression and its subexpressions.
Expression	simplify()	Simplify the expression
protected java.lang.String	tag()	Get the element name used to identify this expression in exported expression format

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

computeCardinality, computeHashCode, computeSpecialProperties, equals, gatherComponents, getImplementationMethod, getItemType, getOperandRole, getStaticUType, getStreamerName, toPattern, typeCheck, unordered

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

explainExtraAttributes, export, getLhs, getLhsExpression, getOperator, getRhs, getRhsExpression, isAssociative, isCommutative, isInverse, operands, setFlattened, setLhsExpression, setRhsExpression, toShortString, toString

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

addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, dispatchTailCall, dynamicError, evaluateAsString, evaluateItem, explain, getCardinality, getConfiguration, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, makeElaborator, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplifyChildren, staticTypeCheck, supportsLazyEvaluation, suppressValidation, typeCheckChildren, typeError, verifyParentPointers, withLocation

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.saxon.trace.Traceable

gatherProperties

Constructor Detail

SingletonIntersectExpression

public SingletonIntersectExpression(Expression p1,
                                    int op,
                                    Expression p2)

Special case of an intersect expression where the first argument is a singleton

Parameters:

p1 - the first argument, always a singleton

op - the operator, always Token.INTERSECT

p2 - the second argument

Method Detail

simplify

public Expression simplify()
                    throws XPathException

Simplify the expression

Overrides:

simplify in class VennExpression

Returns:

the simplified expression (or the original if unchanged, or if modified in-situ)

Throws:

XPathException - if an error is discovered during expression rewriting

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ContextItemStaticInfo 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 VennExpression

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)

copy

public Expression copy(RebindingMap rebindings)

Copy an expression. This makes a deep copy.

Overrides:

copy in class VennExpression

Parameters:

rebindings - variables that need to be re-bound

Returns:

the copy of the original expression

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 VennExpression

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 c)
                              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 VennExpression

Parameters:

c - 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

containsNode

public static boolean containsNode(SequenceIterator iter,
                                   NodeInfo m)
                            throws XPathException

Ask whether the sequence supplied in the first argument contains the node supplied in the second

Parameters:

iter - an iterator over nodes. The iterator will be closed if the node is found.

m - the node to be tested

Returns:

true if (and only if) the sequence contains the node

Throws:

XPathException - if evaluating the iterator fails

getExpressionName

public java.lang.String getExpressionName()

Description copied from class: VennExpression

Get a name identifying the kind of expression, in terms meaningful to a user.

Overrides:

getExpressionName in class VennExpression

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.

displayOperator

protected java.lang.String displayOperator()

Display the operator used by this binary expression

Overrides:

displayOperator in class BinaryExpression

Returns:

String representation of the operator (for diagnostic display only)

tag

protected java.lang.String tag()

Get the element name used to identify this expression in exported expression format

Overrides:

tag in class VennExpression

Returns:

the element name used to identify this expression

getElaborator

public Elaborator getElaborator()

Make an elaborator for this expression

Overrides:

getElaborator in class VennExpression

Returns:

a suitable elaborator