net.sf.saxon.functions

Class ConstantFunction

java.lang.Object

net.sf.saxon.functions.AbstractFunction

net.sf.saxon.functions.SystemFunction

net.sf.saxon.functions.ConstantFunction

All Implemented Interfaces:

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

Modifier and Type	Method and Description
Sequence	call(XPathContext context, Sequence[] arguments) Call the Callable.
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

dependsOnContextItem, dynamicCall, equals, export, exportAdditionalArguments, exportAttributes, fixArguments, getArity, getCardinality, getCompilerName, getContextNode, getDescription, getDetails, getErrorCodeForTypeErrors, getFunctionItemType, getFunctionName, getNetCost, getOperandRoles, getRequiredType, getResultItemType, getResultItemType, getRetainedStaticContext, getSpecialProperties, getStaticBaseUriString, getStreamerName, getUniStringArg, hashCode, importAttributes, isSequenceVariadic, isTrustedResultType, makeCall, makeFunction, makeOptimizedFunctionCall, resultIfEmpty, setArity, setDetails, setRetainedStaticContext, supplyTypeInformation, toShortString, toString, typeCheckCaller

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

atomize, deepEquals, effectiveBooleanValue, getAnnotations, getUnicodeStringValue, isArray, isMap, makeNewContext, simplify, typeCheck

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

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

getGenre

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

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

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

asIterable, concatenate, containsNode, materialize

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

makeRepeatable

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: 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

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.