Package net.sf.saxon.functions

Class ConstantFunction

java.lang.Object

net.sf.saxon.functions.AbstractFunction

net.sf.saxon.functions.ConstantFunction

All Implemented Interfaces:

Callable, FunctionItem, GroundedValue, Item, Sequence

public class ConstantFunction
extends AbstractFunction

A ConstantFunction is a zero-argument function that always delivers the same result, supplied at the time the function is created.

Constructor Summary

Constructors

Constructor	Description
ConstantFunction(GroundedValue value, SequenceType resultType)	Create an anonymous ConstantFunction
ConstantFunction(StructuredQName name, GroundedValue value, SequenceType resultType)	Create a ConstantFunction

Method Summary

Modifier and Type	Method	Description
Sequence	call(XPathContext context, Sequence[] arguments)	Call the Callable.
AnnotationList	getAnnotations()	Get the annotation list
int	getArity()	Get the arity of the function
GroundedValue	getConstantValue()
String	getDescription()	Get a description of this function for use in error messages.
FunctionItemType	getFunctionItemType()	Get the item type of the function item
StructuredQName	getFunctionName()	Get the name of the function, or null if it is anonymous
String	toShortString()	Provide a short string showing the contents of the item, suitable for use in error messages
ConstantFunction	withAnnotationList(AnnotationList annotationList)	Add an annotation list

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

atomize, deepEqual40, deepEquals, effectiveBooleanValue, export, getOperandRoles, getUnicodeStringValue, getUniqueIdentifier, isArray, isMap, isTrustedResultType, makeNewContext, simplify, typeCheck

Methods inherited from class java.lang.Object

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

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

getGenre, isSequenceVariadic

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

asIterable, concatenate, containsNode, materialize

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

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

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

makeRepeatable

Constructor Details

ConstantFunction

public ConstantFunction(StructuredQName name,
 GroundedValue value,
 SequenceType resultType)

Create a ConstantFunction

Parameters:

name - the function name.

value - the value to be returned by the function

resultType - the return type of the function (must match the type of value

ConstantFunction

public ConstantFunction(GroundedValue value,
 SequenceType resultType)

Create an anonymous ConstantFunction

Parameters:

value - the value to be returned by the function

resultType - the return type of the function (must match the type of value

Method Details

withAnnotationList

public ConstantFunction withAnnotationList(AnnotationList annotationList)

Add an annotation list

getAnnotations

public AnnotationList getAnnotations()

Get the annotation list

Specified by:

getAnnotations in interface FunctionItem

Overrides:

getAnnotations in class AbstractFunction

Returns:

the function annotations

getFunctionItemType

public FunctionItemType getFunctionItemType()

Get the item type of the function item

Returns:

the function item's type

getFunctionName

public StructuredQName getFunctionName()

Get the name of the function, or null if it is anonymous

Returns:

the function name, or null for an anonymous inline function

getArity

public int getArity()

Get the arity of the function

Returns:

the number of arguments in the function signature

getDescription

public String getDescription()

Get a description of this function for use in error messages. For named functions, the description is the function name (as a lexical QName). For others, it might be, for example, "inline function", or "partially-applied ends-with function".

Returns:

a description of the function for use in error messages

toShortString

public String toShortString()

Description copied from interface: FunctionItem

Provide a short string showing the contents of the item, suitable for use in error messages

Specified by:

toShortString in interface FunctionItem

Specified by:

toShortString in interface GroundedValue

Specified by:

toShortString in interface Item

Overrides:

toShortString in class AbstractFunction

Returns:

a depiction of the item suitable for use in error messages

call

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

Description copied from interface: Callable

Call the Callable.

Parameters:

context - the dynamic evaluation context

arguments - the values of the arguments, supplied as Sequences.

Generally it is advisable, if calling iterate() to process a supplied sequence, to call it only once; if the value is required more than once, it should first be converted to a GroundedValue by calling the utility method SequenceTool.toGroundedValue().

If the expected value is a single item, the item should be obtained by calling Sequence.head(): it cannot be assumed that the item will be passed as an instance of Item or AtomicValue.

It is the caller's responsibility to perform any type conversions required to convert arguments to the type expected by the callee. An exception is where this Callable is explicitly an argument-converting wrapper around the original Callable.

Returns:

the result of the evaluation, in the form of a Sequence. It is the responsibility of the callee to ensure that the type of result conforms to the expected result type.

Throws:

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

getConstantValue

public GroundedValue getConstantValue()