net.sf.saxon.functions

Class BooleanFn

java.lang.Object

net.sf.saxon.functions.AbstractFunction

net.sf.saxon.functions.SystemFunction

net.sf.saxon.functions.BooleanFn

All Implemented Interfaces:

Callable, Function, GroundedValue, Item, Sequence

public class BooleanFn
extends SystemFunction

This class supports the XPath function boolean()

Constructor Summary

Constructors

Constructor and Description
BooleanFn()

Method Summary

Modifier and Type	Method and Description
BooleanValue	call(XPathContext c, Sequence[] arguments) Call the Callable.
java.lang.String	getCompilerName() Get the (local) name of a class that can be used to generate bytecode for this system function
java.lang.String	getStreamerName() Get a name that identifies the class that can be used to evaluate this function in streaming mode, that is, supplying one item or event at a time as it is delivered by the parser.
Expression	makeFunctionCall(Expression[] arguments) Make an expression that either calls this function, or that is equivalent to a call on this function
static Expression	rewriteEffectiveBooleanValue(Expression exp, ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) Optimize an expression whose effective boolean value is required.
void	supplyTypeInformation(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType, Expression[] arguments) Method called during static type checking.

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

dependsOnContextItem, dynamicCall, equals, export, exportAdditionalArguments, exportAttributes, fixArguments, getArity, getCardinality, getContextNode, getDescription, getDetails, getErrorCodeForTypeErrors, getFunctionItemType, getFunctionName, getIntegerBounds, getNetCost, getOperandRoles, getRequiredType, getResultItemType, getResultItemType, getRetainedStaticContext, getSpecialProperties, getStaticBaseUriString, getUniStringArg, hashCode, importAttributes, isSequenceVariadic, isTrustedResultType, makeCall, makeFunction, makeOptimizedFunctionCall, resultIfEmpty, setArity, setDetails, setRetainedStaticContext, toShortString, toString, typeCheckCaller

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

atomize, deepEquals, effectiveBooleanValue, getAnnotations, getUnicodeStringValue, isArray, isMap, makeNewContext, simplify, typeCheck

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.saxon.om.Function

getGenre

Methods inherited from interface net.sf.saxon.om.Item

getLength, getStringValue, head, isStreamed, itemAt, iterate, reduce, subsequence

Methods inherited from interface net.sf.saxon.om.GroundedValue

asIterable, concatenate, containsNode, materialize

Methods inherited from interface net.sf.saxon.om.Sequence

makeRepeatable

Constructor Detail

BooleanFn

public BooleanFn()

Method Detail

supplyTypeInformation

public void supplyTypeInformation(ExpressionVisitor visitor,
                                  ContextItemStaticInfo contextItemType,
                                  Expression[] arguments)
                           throws XPathException

Description copied from class: SystemFunction

Method called during static type checking. This method may be implemented in subclasses so that functions can take advantage of knowledge of the types of the arguments that will be supplied.

Overrides:

supplyTypeInformation in class SystemFunction

Parameters:

visitor - an expression visitor, providing access to the static context and configuration

contextItemType - information about whether the context item is set, and what its type is

arguments - the expressions appearing as arguments in the function call

Throws:

XPathException - if an error is detected

rewriteEffectiveBooleanValue

public static Expression rewriteEffectiveBooleanValue(Expression exp,
                                                      ExpressionVisitor visitor,
                                                      ContextItemStaticInfo 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

call

public BooleanValue call(XPathContext c,
                         Sequence[] arguments)
                  throws XPathException

Description copied from interface: Callable

Call the Callable.

Parameters:

c - the dynamic evaluation context

arguments - the values of the arguments, supplied as Sequences.

Generally it is advisable, if calling iterate() to process a supplied sequence, to call it only once; if the value is required more than once, it should first be converted to a GroundedValue by calling the utility method SequenceTool.toGroundedValue().

If the expected value is a single item, the item should be obtained by calling Sequence.head(): it cannot be assumed that the item will be passed as an instance of Item or AtomicValue.

It is the caller's responsibility to perform any type conversions required to convert arguments to the type expected by the callee. An exception is where this Callable is explicitly an argument-converting wrapper around the original Callable.

Returns:

the result of the evaluation, in the form of a Sequence. It is the responsibility of the callee to ensure that the type of result conforms to the expected result type.

Throws:

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

makeFunctionCall

public Expression makeFunctionCall(Expression[] arguments)

Description copied from class: SystemFunction

Make an expression that either calls this function, or that is equivalent to a call on this function

Overrides:

makeFunctionCall in class SystemFunction

Parameters:

arguments - the supplied arguments to the function call

Returns:

either a function call on this function, or an expression that delivers the same result

getCompilerName

public java.lang.String getCompilerName()

Description copied from class: SystemFunction

Get the (local) name of a class that can be used to generate bytecode for this system function

Overrides:

getCompilerName in class SystemFunction

Returns:

the name of a bytecode generation class, or null if there is no bytecode support for this function

getStreamerName

public java.lang.String getStreamerName()

Description copied from class: SystemFunction

Get a name that identifies the class that can be used to evaluate this function in streaming mode, that is, supplying one item or event at a time as it is delivered by the parser. Special streaming support is generally available in Saxon-EE for all system functions that take a sequence as their argument.

Overrides:

getStreamerName in class SystemFunction

Returns:

a name that identifies a class that supports streamed evaluation of this system function, or null if no such class is available. The mapping of names to classes is defined in the Saxon-EE class StreamerMap. In non-streaming Saxon editions (HE and PE) the method always returns null.