net.sf.saxon.functions

Class DistinctValues

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.FunctionCall

net.sf.saxon.functions.SystemFunctionCall

net.sf.saxon.functions.CollatingFunction

net.sf.saxon.functions.DistinctValues

All Implemented Interfaces:

Serializable, SourceLocator, LocationProvider, SaxonLocator, Callable, InstructionInfo, Locator

public class DistinctValues
extends CollatingFunction
implements Callable

The XPath 2.0 distinct-values() function

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	DistinctValues.DistinctIterator Iterator class to return the distinct values in a sequence

Field Summary

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

staticCollation

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

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, INHERITED_CONTEXT, INSPECTION_CONTEXT, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, NAVIGATION_CONTEXT, NODE_VALUE_CONTEXT, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, W3C_CONSUMING, W3C_FREE_RANGING, W3C_GROUP_CONSUMING, W3C_MOTIONLESS, WATCH_METHOD

Constructor Summary

Constructors

Constructor and Description
DistinctValues()

Method Summary

Methods

Modifier and Type	Method and Description
Sequence	call(XPathContext context, Sequence[] arguments) Call the Callable.
void	checkArguments(ExpressionVisitor visitor) Method called during static type checking
AtomicComparer	getAtomicComparer() Get the AtomicComparer allocated at compile time.
protected int	getCollationArgument() Get the argument position (0-based) containing the collation name
DistinctValuesAdjunct	getStreamingAdjunct() Get a class that supports streamed evaluation of this expression
SequenceIterator	iterate(XPathContext context) Evaluate the function to return an iteration of selected values or nodes.

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

bindStaticContext, copy, equals, expandCollationURI, getAtomicComparer, getCollator, getCollatorFromLastArgument, getExpressionBaseURI, getPreAllocatedAtomicComparer, getStaticCollation, preAllocateComparer

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

addContextDocumentArgument, addDocToPathMap, computeCardinality, computeSpecialProperties, equalOrNull, getContextNode, getConvertingCallable, getDefaultArgumentNode, getDetails, getErrorCodeForTypeErrors, getFunctionItemType, getImplementationMethod, getItemType, getOperation, getRequiredType, iterateSubExpressionInfo, makeSystemFunction, optimize, 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, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getExpressionCompiler, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getStreamability, getSystemId, getSystemId, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toPattern, toStreamingPattern, typeError

Methods inherited from class java.lang.Object

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

Constructor Detail

DistinctValues

public DistinctValues()

Method Detail

getCollationArgument

protected int getCollationArgument()

Get the argument position (0-based) containing the collation name

Specified by:

getCollationArgument in class CollatingFunction

Returns:

the position of the argument containing the collation URI

checkArguments

public void checkArguments(ExpressionVisitor visitor)
                    throws XPathException

Description copied from class: SystemFunctionCall

Method called during static type checking

Overrides:

checkArguments in class CollatingFunction

Parameters:

visitor - the expression visitor

Throws:

XPathException - if the arguments are incorrect

getAtomicComparer

public AtomicComparer getAtomicComparer()

Get the AtomicComparer allocated at compile time.

Returns:

the AtomicComparer if one has been allocated at compile time; return null if the collation is not known until run-time

getStreamingAdjunct

public DistinctValuesAdjunct getStreamingAdjunct()

Get a class that supports streamed evaluation of this expression

Overrides:

getStreamingAdjunct in class Expression

Returns:

the relevant StreamingAdjunct, or null if none is available

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Evaluate the function to return an iteration of selected values or nodes.

Overrides:

iterate in class Expression

Parameters:

context - supplies the context for evaluation

Returns:

a SequenceIterator that can be used to iterate over the result of the expression

Throws:

XPathException - if any dynamic error occurs evaluating the expression

call

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

Description copied from interface: Callable

Call the Callable.

Specified by:

call in interface Callable

Parameters:

context - 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 methd 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