net.sf.saxon.functions
Class Aggregate

java.lang.Object
  net.sf.saxon.expr.ComputedExpression
      net.sf.saxon.expr.FunctionCall
          net.sf.saxon.functions.SystemFunction
              net.sf.saxon.functions.Aggregate

All Implemented Interfaces:

Container, Expression, InstructionInfoProvider, java.io.Serializable, javax.xml.transform.SourceLocator

public class Aggregate

extends SystemFunction

This class implements the sum(), avg(), count() functions,

See Also:

Serialized Form

Field Summary

static int	AVG
static int	COUNT
static int	SUM

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.ComputedExpression

locationId, staticProperties

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

Aggregate()

Method Summary

void	checkArguments(StaticContext env) Static analysis: prevent sorting of the argument
static int	count(SequenceIterator iter) Get the number of items in a sequence identified by a SequenceIterator
Item	evaluateItem(XPathContext context) Evaluate the function
ItemType	getItemType(TypeHierarchy th) Determine the item type of the value returned by the function
static boolean	isCountFunction(Expression exp) Determine whether a given expression is a call to the count() function

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

addContextDocumentArgument, computeCardinality, computeSpecialProperties, display, getDetails, getErrorCodeForTypeErrors, getRequiredType, main, makeSystemFunction, setDetails, useContextItemAsDefault

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

checkArgumentCount, getDisplayName, getFunctionNameCode, getNumberOfArguments, iterateSubExpressions, optimize, preEvaluate, promote, setArguments, setFunctionNameCode, simplify, simplifyArguments, typeCheck

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

adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, iterate, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, suppressValidation, typeError, typeError

Methods inherited from class java.lang.Object

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

Field Detail

SUM

public static final int SUM

See Also:

Constant Field Values

AVG

public static final int AVG

See Also:

Constant Field Values

COUNT

public static final int COUNT

See Also:

Constant Field Values

Constructor Detail

Aggregate

public Aggregate()

Method Detail

checkArguments

public void checkArguments(StaticContext env)
                    throws XPathException

Static analysis: prevent sorting of the argument

Overrides:

checkArguments in class SystemFunction

Throws:

XPathException

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the item type of the value returned by the function

Specified by:

getItemType in interface Expression

Overrides:

getItemType in class SystemFunction

Parameters:

th -

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the function

Specified by:

evaluateItem in interface Expression

Overrides:

evaluateItem in class ComputedExpression

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

count

public static int count(SequenceIterator iter)
                 throws XPathException

Get the number of items in a sequence identified by a SequenceIterator

Parameters:

iter - The SequenceIterator. This method moves the current position of the supplied iterator; if this isn't safe, make a copy of the iterator first by calling getAnother(). The supplied iterator must be positioned before the first item (there must have been no call on next()).

Returns:

the number of items in the underlying sequence

Throws:

XPathException - if a failure occurs reading the input sequence

isCountFunction

public static boolean isCountFunction(Expression exp)

Determine whether a given expression is a call to the count() function