Package net.sf.saxon.expr
Class BooleanExpression
- java.lang.Object
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- net.sf.saxon.expr.Expression
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- net.sf.saxon.expr.BinaryExpression
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- net.sf.saxon.expr.BooleanExpression
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,LocationProvider
,SaxonLocator
,Negatable
,InstructionInfo
,org.xml.sax.Locator
- Direct Known Subclasses:
AndExpression
,OrExpression
public abstract class BooleanExpression extends BinaryExpression implements Negatable
Boolean expression: two truth values combined using AND or OR.- See Also:
- Serialized Form
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Field Summary
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Fields inherited from class net.sf.saxon.expr.BinaryExpression
operand0, operand1, operator
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Fields inherited from class net.sf.saxon.expr.Expression
EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD
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Constructor Summary
Constructors Constructor Description BooleanExpression(Expression p1, int operator, Expression p2)
Construct a boolean expression
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Method Summary
All Methods Static Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description int
computeCardinality()
Determine the static cardinality.abstract boolean
effectiveBooleanValue(XPathContext c)
Evaluate as a boolean.Item
evaluateItem(XPathContext context)
Evaluate the expressionprotected Expression
forceToBoolean(Expression in, TypeHierarchy th)
java.lang.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 expressionboolean
isNegatable(ExpressionVisitor visitor)
Check whether this specific instance of the expression is negatablestatic void
listAndComponents(Expression exp, java.util.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).abstract Expression
negate()
Return the negation of this boolean expression, that is, an expression that returns true when this expression returns false, and vice versaExpression
optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)
Perform optimisation of an expression and its subexpressions.Expression
typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)
Type-check the expression.-
Methods inherited from class net.sf.saxon.expr.BinaryExpression
computeSpecialProperties, displayOperator, equals, explain, explainExtraAttributes, getArguments, getOperands, getOperator, hashCode, isAssociative, isCommutative, isInverse, iterateSubExpressions, promote, replaceSubExpression, setFlattened, simplify, toString
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Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, copy, doPromotion, dynamicError, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getImplementationMethod, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setLocationId, staticTypeCheck, suppressValidation, typeError
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Constructor Detail
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BooleanExpression
public BooleanExpression(Expression p1, int operator, Expression p2)
Construct a boolean expression
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Method Detail
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getExpressionName
public java.lang.String getExpressionName()
Get a name identifying the kind of expression, in terms meaningful to a user.- Overrides:
getExpressionName
in classExpression
- 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.
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
Description copied from class:BinaryExpression
Type-check the expression. Default implementation for binary operators that accept any kind of operand- Overrides:
typeCheck
in classBinaryExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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 toType.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)
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computeCardinality
public int computeCardinality()
Determine the static cardinality. Returns [1..1]- Overrides:
computeCardinality
in classBinaryExpression
- 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
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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 classBinaryExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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 toType.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)
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forceToBoolean
protected Expression forceToBoolean(Expression in, TypeHierarchy th)
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isNegatable
public boolean isNegatable(ExpressionVisitor visitor)
Check whether this specific instance of the expression is negatable- Specified by:
isNegatable
in interfaceNegatable
- Returns:
- true if it is
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negate
public abstract Expression negate()
Return the negation of this boolean expression, that is, an expression that returns true when this expression returns false, and vice versa
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evaluateItem
public Item evaluateItem(XPathContext context) throws XPathException
Evaluate the expression- Overrides:
evaluateItem
in classExpression
- Parameters:
context
- The context in which the expression is to be evaluated- Returns:
- the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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effectiveBooleanValue
public abstract boolean effectiveBooleanValue(XPathContext c) throws XPathException
Evaluate as a boolean.- Overrides:
effectiveBooleanValue
in classExpression
- 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
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getItemType
public ItemType getItemType(TypeHierarchy th)
Determine the data type of the expression- Specified by:
getItemType
in classExpression
- Parameters:
th
- the type hierarchy cache- Returns:
- BuiltInAtomicType.BOOLEAN
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listAndComponents
public static void listAndComponents(Expression exp, java.util.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 decomposedlist
- the list to which the subexpressions are to be added.
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