net.sf.saxon.functions
Class BooleanFn

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.expr.FunctionCall
          net.sf.saxon.functions.SystemFunction
              net.sf.saxon.functions.BooleanFn

All Implemented Interfaces:

Serializable, SourceLocator, LocationProvider, SaxonLocator, CallableExpression, Negatable, InstructionInfo, Locator

public class BooleanFn
extends SystemFunction
implements Negatable, CallableExpression

This class supports the XPath functions boolean(), not(), true(), and false()

See Also:

Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.functions.SystemFunction

operation

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

argument

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

Constructor Summary

BooleanFn()

Method Summary

SequenceIterator<BooleanValue>	call(SequenceIterator[] arguments, XPathContext c) Evaluate the expression
void	checkArguments(ExpressionVisitor visitor) Static analysis: prevent sorting of the argument
boolean	effectiveBooleanValue(XPathContext c) Evaluate the effective boolean value
Item	evaluateItem(XPathContext context) Evaluate the function
boolean	isNegatable(ExpressionVisitor visitor) Check whether this specific instance of the expression is negatable
Expression	negate() Create an expression that returns the negation of this expression
Expression	optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Perform optimisation of an expression and its subexpressions.
static Expression	rewriteEffectiveBooleanValue(Expression exp, ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Optimize an expression whose effective boolean value is required.

Methods inherited from class net.sf.saxon.functions.SystemFunction

addContextDocumentArgument, addDocToPathMap, computeCardinality, computeSpecialProperties, copy, equals, getDetails, getErrorCodeForTypeErrors, getImplementationMethod, getItemType, getOperation, getRequiredType, makeSystemFunction, setDetails, useContextItemAsDefault

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

addExternalFunctionCallToPathMap, checkArgumentCount, explain, getArguments, getDisplayName, getExpressionName, getFunctionName, getNumberOfArguments, hashCode, iterateSubExpressions, preEvaluate, promote, replaceSubExpression, setArguments, setFunctionName, simplify, simplifyArguments, toString, typeCheck

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

addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, 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, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.saxon.expr.CallableExpression

getArguments

Constructor Detail

BooleanFn

public BooleanFn()

Method Detail

checkArguments

public void checkArguments(ExpressionVisitor visitor)
                    throws XPathException

Static analysis: prevent sorting of the argument

Overrides:

checkArguments in class SystemFunction

Parameters:

visitor - the expression visitor

Throws:

XPathException - if the arguments are incorrect

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 class SystemFunction

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)

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

negate

public Expression negate()

Create an expression that returns the negation of this expression

Specified by:

negate in interface Negatable

Returns:

the negated expression

rewriteEffectiveBooleanValue

public static Expression rewriteEffectiveBooleanValue(Expression exp,
                                                      ExpressionVisitor visitor,
                                                      ExpressionVisitor.ContextItemType contextItemType)
                                               throws XPathException

Optimize an expression whose effective boolean value is required. It is appropriate to apply this rewrite to any expression whose value will be obtained by calling the Expression.effectiveBooleanValue() method (and not otherwise)

Parameters:

exp - the expression whose EBV is to be evaluated

visitor - an expression visitor

contextItemType - the type of the context item for this expression

Returns:

an expression that returns the EBV of exp, or null if no optimization was possible

Throws:

XPathException - if static errors are found

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the function

Overrides:

evaluateItem in class Expression

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

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext c)
                              throws XPathException

Evaluate the effective boolean value

Overrides:

effectiveBooleanValue in class Expression

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

call

public SequenceIterator<BooleanValue> call(SequenceIterator[] arguments,
                                           XPathContext c)
                                    throws XPathException

Description copied from interface: CallableExpression

Evaluate the expression

Specified by:

call in interface CallableExpression

Parameters:

arguments - the values of the arguments, supplied as SequenceIterators

c - the dynamic evaluation context

Returns:

the result of the evaluation, in the form of a SequenceIterator

Throws:

XPathException - if a dynamic error occurs during the evaluation of the expression