net.sf.saxon.expr

Class OrExpression

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.BinaryExpression

net.sf.saxon.expr.BooleanExpression

net.sf.saxon.expr.OrExpression

All Implemented Interfaces:

ExportAgent, Negatable, IdentityComparable

public class OrExpression
extends BooleanExpression

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_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD

Constructor Summary

Constructors

Constructor and Description
OrExpression(Expression p1, Expression p2) Construct a boolean OR expression

Method Summary

Modifier and Type	Method and Description
Expression	copy(RebindingMap rebindings) Copy an expression.
boolean	effectiveBooleanValue(XPathContext c) Evaluate as a boolean.
int	getCost() Return the estimated cost of evaluating an expression.
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, ContextItemStaticInfo contextItemType) Perform optimisation of an expression and its subexpressions.
protected Expression	preEvaluate() Evaluate the expression statically if either or both operands are literals.
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.BooleanExpression

computeCardinality, evaluateItem, forceToBoolean, getExpressionName, getItemType, getOperandRole, getStaticUType, isNegatable, listAndComponents, typeCheck

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

computeHashCode, computeSpecialProperties, displayOperator, equals, explainExtraAttributes, export, getImplementationMethod, 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, dynamicError, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getConstructType, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStreamerName, hasCompatibleStaticContext, hashCode, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isCallOnSystemFunction, isIdentical, isInstruction, isLiftable, isMultiThreaded, isSameExpression, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, typeCheckChildren, typeError, unordered, verifyParentPointers, verifyParentPointers

Methods inherited from class java.lang.Object

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

Constructor Detail

OrExpression

public OrExpression(Expression p1,
                    Expression p2)

Construct a boolean OR expression

Parameters:

p1 - the first operand

p2 - the second operand

Method Detail

preEvaluate

protected Expression preEvaluate()

Description copied from class: BooleanExpression

Evaluate the expression statically if either or both operands are literals. For example, (true() or X) returns true().

Specified by:

preEvaluate in class BooleanExpression

Returns:

a boolean literal if the expression can be evaluated now, or the original expression otherwise.

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 BooleanExpression

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)

getCost

public int getCost()

Description copied from class: Expression

Return the estimated cost of evaluating an expression. This is a very crude measure based on the syntactic form of the expression (we have no knowledge of data values). We take the cost of evaluating a simple scalar comparison or arithmetic expression as 1 (one), and we assume that a sequence has length 5. The resulting estimates may be used, for example, to reorder the predicates in a filter expression so cheaper predicates are evaluated first.

Overrides:

getCost in class Expression

Returns:

an estimate of the gross cost of evaluating the expression, including the cost of evaluating its operands.

copy

public Expression copy(RebindingMap rebindings)

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Parameters:

rebindings -

Returns:

the copy of the original expression

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

Specified by:

negate in class BooleanExpression

Returns:

the negation of this expression

tag

protected java.lang.String tag()

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

Overrides:

tag in class BinaryExpression

Returns:

the element name used to identify this expression

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext c)
                              throws XPathException

Evaluate as a boolean.

Specified by:

effectiveBooleanValue in class BooleanExpression

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