Package net.sf.saxon.functions.hof

Class FunctionLiteral

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.Literal

net.sf.saxon.functions.hof.FunctionLiteral

All Implemented Interfaces:

ExportAgent, Locatable, IdentityComparable, Traceable

public class FunctionLiteral
extends Literal

A FunctionLiteral is a wrapper around a FunctionItem; it is an expression, whose value is the function that it wraps. Note that a FunctionLiteral can be used only where the binding to a specific function is statically known. This works for constructor functions, for system functions that have no context dependency, and for references to user function (my:f#2) in XQuery, but not in XSLT where the reference cannot be fully resolved until separately-compiled packages are linked. In other cases a UserFunctionReference is used.

Field Summary

Fields inherited from class net.sf.saxon.expr.Expression

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_COST, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD

Constructor Summary

Constructors

Constructor	Description
FunctionLiteral(Function value)	Create a literal as a wrapper around a Value

Method Summary

Modifier and Type	Method	Description
int	computeCardinality()	Determine the cardinality
int	computeHashCode()	Return a hash code to support the equals() function
int	computeSpecialProperties()	Compute the static properties of this expression (other than its type).
Expression	copy(RebindingMap rebindings)	Copy an expression.
boolean	equals(java.lang.Object obj)	Determine whether two literals are equal, when considered as expressions.
void	export(ExpressionPresenter out)	Diagnostic print of expression structure.
java.lang.String	getExpressionName()	Get a name identifying the kind of expression, in terms meaningful to a user.
FunctionItemType	getItemType()	Determine the data type of the items in the expression, if possible
Function	getValue()	Get the value represented by this Literal
boolean	isVacuousExpression()	Determine whether this is a vacuous expression as defined in the XQuery update specification
void	setRetainedStaticContext(RetainedStaticContext rsc)	Set the retained static context
Expression	simplify()	Simplify an expression
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)	TypeCheck an expression

Methods inherited from class net.sf.saxon.expr.Literal

addToPathMap, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, exportAtomicValue, exportValue, getDependencies, getImplementationMethod, getIntegerBounds, getNetCost, getStaticUType, getStreamerName, hasEffectiveBooleanValue, isAtomic, isConstantBoolean, isConstantOne, isEmptySequence, isSubtreeExpression, iterate, iterate, makeEmptySequence, makeLiteral, makeLiteral, makeStringsLiteral, optimize, process, toPattern, toShortString, toString

Methods inherited from class net.sf.saxon.expr.Expression

adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, dynamicError, explain, getCardinality, getConfiguration, getCost, getEvaluationMethod, getExtraProperty, getInterpretedExpression, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isUpdatingExpression, markTailFunctionCalls, operandList, operands, operandSparseList, optimizeChildren, prepareForStreaming, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplifyChildren, staticTypeCheck, suppressValidation, typeCheckChildren, typeError, unordered, verifyParentPointers

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.saxon.trace.Traceable

gatherProperties

Constructor Detail

FunctionLiteral

public FunctionLiteral(Function value)

Create a literal as a wrapper around a Value

Parameters:

value - the value of this literal

Method Detail

getValue

public Function getValue()

Get the value represented by this Literal

Overrides:

getValue in class Literal

Returns:

the constant value

simplify

public Expression simplify()
                    throws XPathException

Simplify an expression

Overrides:

simplify in class Expression

Returns:

for a Value, this always returns the value unchanged

Throws:

XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ContextItemStaticInfo contextInfo)
                     throws XPathException

TypeCheck an expression

Overrides:

typeCheck in class Literal

Parameters:

visitor - an expression visitor

contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.

Returns:

for a Value, this always returns the value unchanged

Throws:

XPathException - if an error is discovered during this phase (typically a type error)

getItemType

public FunctionItemType getItemType()

Determine the data type of the items in the expression, if possible

Overrides:

getItemType in class Literal

Returns:

for the default implementation: AnyItemType (not known)

computeCardinality

public int computeCardinality()

Determine the cardinality

Overrides:

computeCardinality in class Literal

Returns:

the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE. May also return StaticProperty.ALLOWS_ZERO if the result is known to be an empty sequence, or StaticProperty.ALLOWS_MANY if if is known to return a sequence of length two or more.

computeSpecialProperties

public int computeSpecialProperties()

Compute the static properties of this expression (other than its type). For a Value, the only special property is StaticProperty.NO_NODES_NEWLY_CREATED.

Overrides:

computeSpecialProperties in class Literal

Returns:

the value StaticProperty.NO_NODES_NEWLY_CREATED

isVacuousExpression

public boolean isVacuousExpression()

Determine whether this is a vacuous expression as defined in the XQuery update specification

Overrides:

isVacuousExpression in class Literal

Returns:

true if this expression is vacuous

copy

public Expression copy(RebindingMap rebindings)

Copy an expression. This makes a deep copy.

Overrides:

copy in class Literal

Parameters:

rebindings -

Returns:

the copy of the original expression

setRetainedStaticContext

public void setRetainedStaticContext(RetainedStaticContext rsc)

Set the retained static context

Overrides:

setRetainedStaticContext in class Expression

Parameters:

rsc - the static context to be retained

equals

public boolean equals(java.lang.Object obj)

Determine whether two literals are equal, when considered as expressions.

Overrides:

equals in class Literal

Parameters:

obj - the other expression

Returns:

true if the two literals are equal. The test here requires (a) identity in the sense defined by XML Schema (same value in the same value space), and (b) identical type annotations. For example the literal xs:int(3) is not equal (as an expression) to xs:short(3), because the two expressions are not interchangeable.

computeHashCode

public int computeHashCode()

Return a hash code to support the equals() function

Overrides:

computeHashCode in class Literal

Returns:

a computed hash code

getExpressionName

public java.lang.String getExpressionName()

Get a name identifying the kind of expression, in terms meaningful to a user.

Overrides:

getExpressionName in class Literal

Returns:

a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in export() output displaying the expression.

export

public void export(ExpressionPresenter out)
            throws XPathException

Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Specified by:

export in interface ExportAgent

Overrides:

export in class Literal

Parameters:

out - the expression presenter used to display the structure

Throws:

XPathException - if the export fails, for example if an expression is found that won't work in the target environment.