net.sf.saxon.functions

Class BooleanFn

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

public class BooleanFn
extends SystemFunction
implements Negatable

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

Field Summary

static int
BOOLEAN
static int
FALSE
static int
NOT
static int
TRUE

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD, locationId, staticProperties

Method Summary

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, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
static Expression
rewriteEffectiveBooleanValue(Expression exp, ExpressionVisitor visitor, ItemType contextItemType)
Optimize an expression whose effective boolean value is required
Expression
simplify(ExpressionVisitor visitor)
Simplify the function call.

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

addContextDocumentArgument, addDocToPathMap, checkArguments, computeCardinality, computeSpecialProperties, copy, getDetails, getErrorCodeForTypeErrors, getItemType, getRequiredType, makeSystemFunction, optimize, setDetails, useContextItemAsDefault

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

addExternalFunctionCallToPathMap, checkArgumentCount, checkArguments, equals, explain, getArguments, getDisplayName, getFunctionName, getNumberOfArguments, hashCode, iterateSubExpressions, optimize, preEvaluate, promote, replaceSubExpression, setArguments, setFunctionName, simplify, simplifyArguments, 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

Field Details

BOOLEAN

public static final int BOOLEAN
Field Value:
0

FALSE

public static final int FALSE
Field Value:
3

NOT

public static final int NOT
Field Value:
1

TRUE

public static final int TRUE
Field Value:
2

Method Details

checkArguments

public void checkArguments(ExpressionVisitor visitor)
            throws XPathException
Static analysis: prevent sorting of the argument
Overrides:
checkArguments in interface SystemFunction

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext c)
            throws XPathException
Evaluate the effective boolean value
Overrides:
effectiveBooleanValue in interface Expression

evaluateItem

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

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

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 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)

rewriteEffectiveBooleanValue

public static Expression rewriteEffectiveBooleanValue(Expression exp,
                                                      ExpressionVisitor visitor,
                                                      ItemType contextItemType)
            throws XPathException
Optimize an expression whose effective boolean value is required
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

simplify

public Expression simplify(ExpressionVisitor visitor)
            throws XPathException
Simplify the function call. Default method is to simplify each of the supplied arguments and evaluate the function if all are now known.
Overrides:
simplify in interface FunctionCall
Parameters:
visitor - an expression visitor