net.sf.saxon.functions

Class ConstantFunction

java.lang.Object

net.sf.saxon.om.AbstractItem

net.sf.saxon.functions.AbstractFunction

net.sf.saxon.functions.SystemFunction

net.sf.saxon.functions.ConstantFunction

All Implemented Interfaces:

PullEvent, Callable, Function, GroundedValue, Item, Sequence

Direct Known Subclasses:

ConstantFunction.False, ConstantFunction.True

public class ConstantFunction
extends SystemFunction

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

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ConstantFunction.False
static class	ConstantFunction.True

Field Summary

Fields

Modifier and Type	Field and Description
GroundedValue	value

Constructor Summary

Constructors

Constructor and Description
ConstantFunction(GroundedValue value)

Method Summary

Methods

Modifier and Type	Method and Description
Sequence	call(XPathContext context, Sequence[] arguments) Invoke the function
IntegerValue[]	getIntegerBounds() For a function 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.
Expression	makeFunctionCall(Expression[] arguments) Make an expression that either calls this function, or that is equivalent to a call on this function

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

equals, export, exportAttributes, getArity, getCardinality, getContextNode, getDescription, getDetails, getErrorCodeForTypeErrors, getExpressionCompiler, getFunctionItemType, getFunctionName, 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

value

public GroundedValue value

Constructor Detail

ConstantFunction

public ConstantFunction(GroundedValue value)

Method Detail

call

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

Description copied from interface: Function

Invoke the function

Parameters:

context - the XPath dynamic evaluation context

arguments - the actual arguments to be supplied

Returns:

the result of invoking the function

Throws:

XPathException - if a dynamic error occurs within the function

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

getIntegerBounds

public IntegerValue[] getIntegerBounds()

Description copied from class: SystemFunction

For a function 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.