net.sf.saxon.functions

Class Count

java.lang.Object

net.sf.saxon.om.AbstractItem

net.sf.saxon.functions.AbstractFunction

net.sf.saxon.functions.SystemFunction

net.sf.saxon.functions.FoldingFunction

net.sf.saxon.functions.Count

All Implemented Interfaces:

PullEvent, Callable, Function, GroundedValue, Item, Sequence

public class Count
extends FoldingFunction

Implementation of the fn:count function

Constructor Summary

Constructors

Constructor and Description
Count()

Method Summary

Methods

Modifier and Type	Method and Description
IntegerValue	call(XPathContext context, Sequence[] arguments) Evaluate the expression
static int	count(SequenceIterator iter) Get the number of items in a sequence identified by a SequenceIterator
ExpressionCompiler	getExpressionCompiler() Return the compiler of the Sum expression
Fold	getFold(XPathContext context, Sequence... additionalArguments) Create the Fold object which actually performs the evaluation.
IntegerValue[]	getIntegerBounds() For an expression that returns an integer or a sequence of integers, get a lower and upper bound on the values of the integers that may be returned, from static analysis.
CountAdjunct	getStreamingAdjunct() Get a class that supports streamed evaluation of this expression

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

equals, export, exportAttributes, getArity, getCardinality, getContextNode, getDescription, getDetails, getErrorCodeForTypeErrors, getFunctionItemType, getFunctionName, getOperandRoles, getRequiredType, getResultItemType, getResultItemType, getRetainedStaticContext, getSpecialProperties, getStaticBaseUriString, importAttributes, makeCall, makeFunction, makeFunctionCall, makeOptimizedFunctionCall, resultIfEmpty, setArity, setDetails, setRetainedStaticContext, supplyTypeInformation, typeCheckCaller

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

atomize, deepEquals, effectiveBooleanValue, getStringValue, getStringValueCS, isArray, isMap, optimize, simplify, typeCheck

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

getLength, head, 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

Count

public Count()

Method Detail

getIntegerBounds

public IntegerValue[] getIntegerBounds()

For an expression that returns an integer or a sequence of integers, get a lower and upper bound on the values of the integers that may be returned, from static analysis. The default implementation returns null, meaning "unknown" or "not applicable". Other implementations return an array of two IntegerValue objects, representing the lower and upper bounds respectively. The values UNBOUNDED_LOWER and UNBOUNDED_UPPER are used by convention to indicate that the value may be arbitrarily large. The values MAX_STRING_LENGTH and MAX_SEQUENCE_LENGTH are used to indicate values limited by the size of a string or the size of a sequence.

Overrides:

getIntegerBounds in class SystemFunction

Returns:

the lower and upper bounds of integer values in the result, or null to indicate unknown or not applicable.

getFold

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

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

Specified by:

getFold in class FoldingFunction

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

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

call

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

Evaluate the expression

Specified by:

call in interface Callable

Specified by:

call in interface Function

Overrides:

call in class FoldingFunction

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

getStreamingAdjunct

public CountAdjunct getStreamingAdjunct()

Get a class that supports streamed evaluation of this expression

Overrides:

getStreamingAdjunct in class FoldingFunction

Returns:

the relevant StreamingAdjunct, or null if none is available

getExpressionCompiler

public ExpressionCompiler getExpressionCompiler()

Return the compiler of the Sum expression

Overrides:

getExpressionCompiler in class SystemFunction

Returns:

the relevant ExpressionCompiler