net.sf.saxon.expr

Class VennExpression

Implemented Interfaces:
EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, SourceLocator

public class VennExpression
extends BinaryExpression

An expression representing a nodeset that is a union, difference, or intersection of two other NodeSets

Field Summary

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

operand0, operand1, operator

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD, locationId, staticProperties

Constructor Summary

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

Method Summary

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.
ItemType
getItemType(TypeHierarchy th)
Determine the data type of the items returned by this expression
int
hashCode()
Is this expression the same as another expression?
SequenceIterator
iterate(XPathContext c)
Iterate over the value of the expression.
Expression
optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
Expression
simplify(ExpressionVisitor visitor)
Simplify the expression
Expression
typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression

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

computeCardinality, computeSpecialProperties, displayOperator, equals, explain, getOperands, getOperator, hashCode, isAssociative, isCommutative, isInverse, iterateSubExpressions, optimize, promote, replaceSubExpression, setFlattened, simplify, toString, typeCheck

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

addToPathMap, adoptChildExpression, checkPermittedContents, computeCardinality, computeDependencies, computeSpecialProperties, computeStaticProperties, copy, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, explain, explain, findParentOf, getCardinality, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getItemType, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, iterateSubExpressions, markTailFunctionCalls, optimize, process, promote, replaceSubExpression, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, simplify, staticTypeCheck, suppressValidation, toString, typeCheck, typeError

Constructor Details

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 Details

computeCardinality

public final int computeCardinality()
Determine the static cardinality of the expression
Overrides:
computeCardinality in interface BinaryExpression

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 interface BinaryExpression

copy

public Expression copy()
Copy an expression. This makes a deep copy.
Overrides:
copy in interface Expression
Returns:
the copy of the original 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 interface Expression

getItemType

public final ItemType getItemType(TypeHierarchy th)
Determine the data type of the items returned by this expression
Overrides:
getItemType in interface Expression
Parameters:
th - the type hierarchy cache
Returns:
the data type

hashCode

public int hashCode()
Is this expression the same as another expression?
Overrides:
hashCode in interface BinaryExpression

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
Specified by:
iterate in interface SequenceIterable
Overrides:
iterate in interface Expression
Parameters:
c - The context for evaluation
Returns:
a SequenceIterator representing the union of the two operands

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ItemType 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 interface 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)

simplify

public Expression simplify(ExpressionVisitor visitor)
            throws XPathException
Simplify the expression
Overrides:
simplify in interface BinaryExpression
Parameters:
visitor - an expression visitor

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
            throws XPathException
Type-check the expression
Overrides:
typeCheck in interface BinaryExpression