net.sf.saxon.functions

Class FoldingFunction

java.lang.Object

net.sf.saxon.om.AbstractItem

net.sf.saxon.functions.AbstractFunction

net.sf.saxon.functions.SystemFunction

net.sf.saxon.functions.FoldingFunction

All Implemented Interfaces:

Callable, Function, GroundedValue, Item, Sequence

Direct Known Subclasses:

ArrayFunctionSet.ArrayFromSequence, Average, FoldLeftFn, StringJoin, Sum

public abstract class FoldingFunction
extends SystemFunction

Implementation of aggregate functions such as sum() and avg() that supply a fold() function. Such functions are automatically streamable.

Constructor Summary

Constructors

Constructor and Description
FoldingFunction()

Method Summary

Modifier and Type	Method and Description
Sequence	call(XPathContext context, Sequence[] arguments) Evaluate the expression
abstract Fold	getFold(XPathContext context, Sequence... additionalArguments) Create the Fold object which actually performs the evaluation.
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.

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

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

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

atomize, deepEquals, effectiveBooleanValue, getAnnotations, getStringValue, getStringValueCS, isArray, isMap, makeNewContext, simplify, typeCheck

Methods inherited from class net.sf.saxon.om.AbstractItem

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

Methods inherited from class java.lang.Object

clone, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

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

iterate

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

head

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

getLength, head, itemAt, reduce, subsequence

Constructor Detail

FoldingFunction

public FoldingFunction()

Method Detail

getFold

public abstract Fold getFold(XPathContext context,
                             Sequence... additionalArguments)
                      throws XPathException

Create the Fold object which actually performs the evaluation. Must be implemented in every subclass.

Parameters:

context - the dynamic evaluation context

additionalArguments - the values of all arguments other than the first.

Returns:

the Fold object used to compute the function

Throws:

XPathException - if a dynamic error occurs

call

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

Evaluate the expression

Parameters:

context - the dynamic evaluation context

arguments - the values of the arguments, supplied as Sequences

Returns:

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

Throws:

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

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.