net.sf.saxon.functions

Class PositionAndLast

java.lang.Object

net.sf.saxon.om.AbstractItem

net.sf.saxon.functions.AbstractFunction

net.sf.saxon.functions.SystemFunction

net.sf.saxon.functions.ContextAccessorFunction

net.sf.saxon.functions.PositionAndLast

All Implemented Interfaces:

Callable, Function, GroundedValue, Item, Sequence

Direct Known Subclasses:

PositionAndLast.Last, PositionAndLast.Position

public abstract class PositionAndLast
extends ContextAccessorFunction

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	PositionAndLast.Last
static class	PositionAndLast.Position

Constructor Summary

Constructors

Constructor and Description
PositionAndLast()

Method Summary

Modifier and Type	Method and Description
Function	bindContext(XPathContext context) Bind a context item to appear as part of the function's closure.
IntegerValue	call(XPathContext context, Sequence[] arguments) Evaluate the expression
abstract Int64Value	evaluateItem(XPathContext c) Evaluate in a general context
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.
int	getNetCost() Get an estimate of the net cost of evaluating the function, excluding the cost of evaluating its arguments.
boolean	isContextPossiblyUndefined() Ask whether the context item may possibly be undefined
void	supplyTypeInformation(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo, 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, getCompilerName, getContextNode, getDescription, getDetails, getErrorCodeForTypeErrors, getFunctionItemType, getFunctionName, getOperandRoles, getRequiredType, getResultItemType, getResultItemType, getRetainedStaticContext, getSpecialProperties, getStaticBaseUriString, getStreamerName, importAttributes, isTrustedResultType, makeCall, makeFunction, makeFunctionCall, makeOptimizedFunctionCall, resultIfEmpty, setArity, setDetails, setRetainedStaticContext, 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

PositionAndLast

public PositionAndLast()

Method Detail

getNetCost

public int getNetCost()

Get an estimate of the net cost of evaluating the function, excluding the cost of evaluating its arguments. The result is 0 for very simple functions like position() and exists(), 1 by default, and higher values for particularly expensive functions.

Overrides:

getNetCost in class SystemFunction

Returns:

the estimated cost

bindContext

public Function bindContext(XPathContext context)
                     throws XPathException

Bind a context item to appear as part of the function's closure. If this method has been called, the supplied context item will be used in preference to the context item at the point where the function is actually called.

Specified by:

bindContext in class ContextAccessorFunction

Parameters:

context - the context to which the function applies. Must not be null.

Throws:

XPathException

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.

supplyTypeInformation

public void supplyTypeInformation(ExpressionVisitor visitor,
                                  ContextItemStaticInfo contextInfo,
                                  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

contextInfo - 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

isContextPossiblyUndefined

public boolean isContextPossiblyUndefined()

Ask whether the context item may possibly be undefined

Returns:

true if it might be undefined

evaluateItem

public abstract Int64Value evaluateItem(XPathContext c)
                                 throws XPathException

Evaluate in a general context

Throws:

XPathException

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 ContextAccessorFunction

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