net.sf.saxon.expr

Class BooleanExpression

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

public class BooleanExpression
extends BinaryExpression
implements Negatable

Boolean expression: two truth values combined using AND or OR.

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

BooleanExpression(Expression p1, int operator, Expression p2)
Construct a boolean expression

Method Summary

int
computeCardinality()
Determine the static cardinality.
Expression
copy()
Copy an expression.
boolean
effectiveBooleanValue(XPathContext c)
Evaluate as a boolean.
Item
evaluateItem(XPathContext context)
Evaluate the expression
ItemType
getItemType(TypeHierarchy th)
Determine the data type of the expression
boolean
isNegatable(ExpressionVisitor visitor)
Check whether this specific instance of the expression is negatable
static void
listAndComponents(Expression exp, List list)
Construct a list containing the "anded" subexpressions of an expression: if the expression is (A and B and C), this returns (A, B, C).
Expression
negate()
Return the negation of this boolean expression, that is, an expression that returns true when this expression returns false, and vice versa
Expression
optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
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

BooleanExpression

public BooleanExpression(Expression p1,
                         int operator,
                         Expression p2)
Construct a boolean expression
Parameters:
p1 - the first operand
operator - one of Token.AND or Token.OR
p2 - the second operand

Method Details

computeCardinality

public int computeCardinality()
Determine the static cardinality. Returns [1..1]
Overrides:
computeCardinality 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 c)
            throws XPathException
Evaluate as a boolean.
Overrides:
effectiveBooleanValue in interface Expression

evaluateItem

public Item evaluateItem(XPathContext context)
            throws XPathException
Evaluate the expression
Specified by:
evaluateItem in interface EvaluableItem
Overrides:
evaluateItem in interface Expression

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the expression
Overrides:
getItemType in interface Expression
Parameters:
th - the type hierarchy cache
Returns:
BuiltInAtomicType.BOOLEAN

isNegatable

public boolean isNegatable(ExpressionVisitor visitor)
Check whether this specific instance of the expression is negatable
Specified by:
isNegatable in interface Negatable
Returns:
true if it is

listAndComponents

public static void listAndComponents(Expression exp,
                                     List list)
Construct a list containing the "anded" subexpressions of an expression: if the expression is (A and B and C), this returns (A, B, C).
Parameters:
exp - the expression to be decomposed
list - the list to which the subexpressions are to be added.

negate

public Expression negate()
Return the negation of this boolean expression, that is, an expression that returns true when this expression returns false, and vice versa
Specified by:
negate in interface Negatable
Returns:
the negation of this expression

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)

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
            throws XPathException
Type-check the expression. Default implementation for binary operators that accept any kind of operand
Overrides:
typeCheck in interface BinaryExpression