com.saxonica.functions.hof

Class FunctionLookup

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.FunctionCall

net.sf.saxon.functions.SystemFunctionCall

com.saxonica.functions.hof.FunctionLookup

All Implemented Interfaces:

SourceLocator, Callable, IdentityComparable, InstructionInfo

public class FunctionLookup
extends SystemFunctionCall
implements Callable

This class supports the function-lookup() function in XPath 3.0. It takes as arguments a function name (QName) and arity, and returns a function item representing that function if found, or an empty sequence if not found.

Field Summary

Fields inherited from class net.sf.saxon.functions.SystemFunctionCall

operation

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

argument

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

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

Constructor Summary

Constructors

Constructor and Description
FunctionLookup()

Method Summary

Methods

Modifier and Type	Method and Description
void	bindStaticContext(StaticContext env) Bind aspects of the static context on which the particular function depends
Sequence	call(XPathContext context, Sequence[] arguments) Evaluate the expression
FunctionLookup	copy() Copy an expression.
boolean	equals(Object o) Determine whether two expressions are equivalent
FunctionItem	evaluateItem(XPathContext context) Run-time evaluation.
int	getIntrinsicDependencies() Determine the intrinsic dependencies
FunctionItem	lookup(StructuredQName name, int arity, XPathContext context)
Expression	preEvaluate(ExpressionVisitor visitor) Pre-evaluate a function at compile time.

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

addContextDocumentArgument, addDocToPathMap, checkArguments, computeCardinality, computeSpecialProperties, equalOrNull, getContextNode, getConvertingCallable, getDefaultArgumentNode, getDetails, getErrorCodeForTypeErrors, getFunctionItemType, getImplementationMethod, getItemType, getOperation, getRequiredType, makeSystemFunction, operands, optimize, setDetails, toShortString, useContextItemAsDefault

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

addExternalFunctionCallToPathMap, checkArgumentCount, explain, getArguments, getDisplayName, getExpressionName, getFunctionName, getNumberOfArguments, hashCode, promote, replaceOperand, setArguments, setFunctionName, simplifyArguments, toString, typeCheck

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

addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, clearStreamabilityData, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getConfiguration, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExpressionCompiler, getHostLanguage, getIntegerBounds, getLineNumber, getLocationId, getObjectName, getPosture, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getStreamability, getStreamingAdjunct, getSweep, getSystemId, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isIdentical, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, iterateEvents, makeStreamingAdjunct, markTailFunctionCalls, operandList, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, setPostureAndSweep, simplify, staticTypeCheck, suppressValidation, toPattern, toStreamingPattern, typeError, unordered

Methods inherited from class java.lang.Object

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

Constructor Detail

FunctionLookup

public FunctionLookup()

Method Detail

bindStaticContext

public void bindStaticContext(StaticContext env)
                       throws XPathException

Description copied from class: SystemFunctionCall

Bind aspects of the static context on which the particular function depends

Overrides:

bindStaticContext in class SystemFunctionCall

Parameters:

env - the static context of the function call

Throws:

XPathException - if execution with this static context will inevitably fail

getIntrinsicDependencies

public int getIntrinsicDependencies()

Determine the intrinsic dependencies

Overrides:

getIntrinsicDependencies in class Expression

Returns:

a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty

preEvaluate

public Expression preEvaluate(ExpressionVisitor visitor)
                       throws XPathException

Description copied from class: FunctionCall

Pre-evaluate a function at compile time. Functions that do not allow pre-evaluation, or that need access to context information, can override this method.

Overrides:

preEvaluate in class FunctionCall

Parameters:

visitor - an expression visitor

Returns:

the result of the early evaluation, or the original expression, or potentially a simplified expression

Throws:

XPathException - if evaluation fails

copy

public FunctionLookup copy()

Description copied from class: SystemFunctionCall

Copy an expression. This makes a deep copy.

Overrides:

copy in class SystemFunctionCall

Returns:

the copy of the original expression

equals

public boolean equals(Object o)

Determine whether two expressions are equivalent

Overrides:

equals in class SystemFunctionCall

evaluateItem

public FunctionItem evaluateItem(XPathContext context)
                          throws XPathException

Run-time evaluation. This is the only thing in the spec that requires information about in-scope functions to be available at run-time. However, we keep it because it's handy for some other things such as saxon:evaluate().

Overrides:

evaluateItem in class Expression

Parameters:

context - The context in which the expression is to be evaluated

Returns:

the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence

Throws:

XPathException - if any dynamic error occurs evaluating the expression

lookup

public FunctionItem lookup(StructuredQName name,
                  int arity,
                  XPathContext context)
                    throws XPathException

Throws:

XPathException

call

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

Evaluate the expression

Specified by:

call in interface Callable

Parameters:

context - the dynamic evaluation context

arguments - the values of the arguments, supplied as SequenceIterators

Returns:

the result of the evaluation, in the form of a SequenceIterator

Throws:

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