net.sf.saxon.functions

Class ScalarSystemFunction

java.lang.Object

net.sf.saxon.om.AbstractItem

net.sf.saxon.functions.AbstractFunction

net.sf.saxon.functions.SystemFunction

net.sf.saxon.functions.ScalarSystemFunction

All Implemented Interfaces:

PullEvent, Callable, Function, GroundedValue, Item, Sequence

Direct Known Subclasses:

Abs, AccessorFn, Ceiling, DocumentUri_1, EncodeForUri, EscapeHtmlUri, Floor, GenerateId_1, IriToUri, LocalName_1, LowerCase, Name_1, NamespaceUri_1, NodeName_1, NormalizeSpace_1, Number_1, Path_1, String_1, StringLength_1, UpperCase

public abstract class ScalarSystemFunction
extends SystemFunction

A Scalar system function is a pure function that accepts a single item as its operand, returns a single atomic value as its result, typically returns an empty sequence if the argument is an empty sequence, and has no context dependencies.

Field Summary

Fields

Modifier and Type	Field and Description
static ZeroOrOne<StringValue>	ZERO_LENGTH_STRING Static constant representing a zero-length string

Constructor Summary

Constructors

Constructor and Description
ScalarSystemFunction()

Method Summary

Methods

Modifier and Type	Method and Description
ZeroOrOne<? extends AtomicValue>	call(XPathContext context, Sequence[] arguments) Evaluate the expression
abstract AtomicValue	evaluate(Item arg, XPathContext context) Abstract method that must be supplied in subclasses to perform the evaluation
Expression	makeFunctionCall(Expression[] arguments) Make an expression that either calls this function, or that is equivalent to a call on this function
ZeroOrOne<? extends AtomicValue>	resultWhenEmpty() Method that may be supplied in subclasses, to indicate the result that is returned when an empty sequence is supplied as the argument value.

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

equals, export, exportAttributes, getArity, getCardinality, getContextNode, getDescription, getDetails, getErrorCodeForTypeErrors, getExpressionCompiler, getFunctionItemType, getFunctionName, getIntegerBounds, getOperandRoles, getRequiredType, getResultItemType, getResultItemType, getRetainedStaticContext, getSpecialProperties, getStaticBaseUriString, getStreamingAdjunct, importAttributes, makeCall, makeFunction, 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

Field Detail

ZERO_LENGTH_STRING

public static final ZeroOrOne<StringValue> ZERO_LENGTH_STRING

Static constant representing a zero-length string

Constructor Detail

ScalarSystemFunction

public ScalarSystemFunction()

Method Detail

evaluate

public abstract AtomicValue evaluate(Item arg,
                   XPathContext context)
                              throws XPathException

Abstract method that must be supplied in subclasses to perform the evaluation

Parameters:

arg - the supplied argument

context - the dynamic context

Returns:

the result of the evaluation

Throws:

XPathException - if a dynamic error occurs

resultWhenEmpty

public ZeroOrOne<? extends AtomicValue> resultWhenEmpty()

Method that may be supplied in subclasses, to indicate the result that is returned when an empty sequence is supplied as the argument value. The default is to return the empty sequence

Returns:

the result of evaluation when the supplied argument is an empty sequence

call

public final ZeroOrOne<? extends AtomicValue> 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

makeFunctionCall

public Expression makeFunctionCall(Expression[] arguments)

Description copied from class: SystemFunction

Make an expression that either calls this function, or that is equivalent to a call on this function

Overrides:

makeFunctionCall in class SystemFunction

Parameters:

arguments - the supplied arguments to the function call

Returns:

either a function call on this function, or an expression that delivers the same result