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:

java.io.Serializable, javax.xml.transform.SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, Negatable, SequenceIterable, InstructionInfo, org.xml.sax.Locator
```
public class BooleanFn
extends SystemFunction
implements Negatable
```
This class supports the XPath functions boolean(), not(), true(), and false()

See Also:

Serialized Form

Field Summary

Fields
Modifier and Type Field Description

static int BOOLEAN

static int FALSE

static int NOT

static int TRUE
- Fields inherited from class net.sf.saxon.expr.Expression
  EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
- Fields inherited from class net.sf.saxon.expr.FunctionCall
  argument
- Fields inherited from class net.sf.saxon.functions.SystemFunction
  operation

Fields
Modifier and Type	Field	Description
`static int`	`BOOLEAN`
`static int`	`FALSE`
`static int`	`NOT`
`static int`	`TRUE`

Constructor Summary

Constructors
Constructor Description

BooleanFn()

Constructors
Constructor	Description
`BooleanFn()`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`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.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, dynamicError, evaluateAsString, evaluatePendingUpdates, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isUpdatingExpression, iterate, iterateEvents, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError

Methods inherited from class net.sf.saxon.expr.FunctionCall
addExternalFunctionCallToPathMap, checkArgumentCount, equals, explain, getArguments, getDisplayName, getFunctionName, getNumberOfArguments, hashCode, iterateSubExpressions, preEvaluate, promote, replaceSubExpression, setArguments, setFunctionName, simplifyArguments, toString, typeCheck

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from class net.sf.saxon.functions.SystemFunction
addContextDocumentArgument, addDocToPathMap, computeCardinality, computeSpecialProperties, copy, getDetails, getErrorCodeForTypeErrors, getItemType, getRequiredType, makeSystemFunction, setDetails, useContextItemAsDefault

- Field Detail
  - BOOLEAN
```
public static final int BOOLEAN
```
    See Also:
    
    Constant Field Values
  - NOT
```
public static final int NOT
```
    See Also:
    
    Constant Field Values
  - TRUE
```
public static final int TRUE
```
    See Also:
    
    Constant Field Values
  - FALSE
```
public static final int FALSE
```
    See Also:
    
    Constant Field Values
- Constructor Detail
  - BooleanFn
```
public BooleanFn()
```
- Method Detail
  - 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 class FunctionCall
    
    Parameters:
    
    visitor - an expression visitor
    
    Returns:
    
    the simplified expression
    
    Throws:
    
    XPathException - if an error is discovered during expression rewriting
  - 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
  - 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 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,
                                                      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
  - evaluateItem
```
public Item evaluateItem(XPathContext context)
                  throws XPathException
```
    Evaluate the function
    
    Specified by:
    
    evaluateItem in interface EvaluableItem
    
    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

Class BooleanFn

Field Summary

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

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

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

Constructor Summary

Method Summary

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

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

Methods inherited from class java.lang.Object

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

Field Detail

BOOLEAN

NOT

TRUE

FALSE

Constructor Detail

BooleanFn

Method Detail

simplify

checkArguments

optimize

isNegatable

negate

rewriteEffectiveBooleanValue

evaluateItem

effectiveBooleanValue