net.sf.saxon.expr

Class FunctionCall

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.FunctionCall

All Implemented Interfaces:

ExportAgent, IdentityComparable

Direct Known Subclasses:

IntegratedFunctionCall, JavaExtensionFunctionCall, JavaExtensionLibrary.UnresolvedExtensionFunctionCall, StaticFunctionCall, UserFunctionCall, XPathFunctionCall

public abstract class FunctionCall
extends Expression

Abstract superclass for calls to system-defined and user-defined functions

Field Summary

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

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

Constructor Summary

Constructors

Constructor and Description
FunctionCall()

Method Summary

Modifier and Type	Method and Description
PathMap.PathMapNodeSet	addExternalFunctionCallToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodes) Add a representation of this expression to a PathMap.
boolean	adjustRequiredType(JavaExternalObjectType requiredType) When a call to a Java extension function appears in a context where there the required type is a Java external object (typically an xsl:variable with a declared type, or as an argument to another Java extension function), notify this required type so that the process of converting the result to an XDM value can be short-circuited.
protected int	checkArgumentCount(int min, int max) Check number of arguments.
protected void	checkArguments(ExpressionVisitor visitor) Method supplied by each class of function to check arguments during parsing, when all the argument expressions have been read
void	checkFunctionCall(Function target, ExpressionVisitor visitor) Check the function call against the declared function signature, applying the function conversion rules to each argument as necessary
int	computeHashCode() Get hashCode in support of equals() method
boolean	equals(java.lang.Object o) Determine whether two expressions are equivalent
Sequence[]	evaluateArguments(XPathContext context)
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
Expression	getArg(int n) Get the expression supplied as the Nth argument
Expression[]	getArguments() Get the expressions supplied as actual arguments to the function
int	getArity() Determine the number of actual arguments supplied in the function call
java.lang.String	getDisplayName() Get the name of the function for display in messages
java.lang.String	getExpressionName() Get a name identifying the kind of expression, in terms meaningful to a user.
abstract StructuredQName	getFunctionName() Get the qualified of the function being called
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
int	getNetCost() Return the estimated cost of evaluating an expression.
OperandArray	getOperanda() Get the data structure holding the operands of this expression.
abstract Function	getTargetFunction(XPathContext context) Get the target function to be called
SequenceIterator	iterate(XPathContext context) Return an Iterator to iterate over the values of a sequence.
java.lang.Iterable<Operand>	operands() Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) Perform optimisation of an expression and its subexpressions.
static java.lang.String	pluralArguments(int num) Utility routine used in constructing error messages: get the word "argument" or "arguments"
Expression	preEvaluate(ExpressionVisitor visitor) Pre-evaluate a function at compile time.
protected Expression	preEvaluateIfConstant(ExpressionVisitor visitor)
void	setArg(int n, Expression child) Set the expression to be used as the Nth argument
void	setArguments(Expression[] args) Method called by the expression parser when all arguments have been supplied
protected void	setOperanda(Expression[] args, OperandRole[] roles)
protected void	setOperanda(OperandArray operanda) Set the data structure for the operands of this expression.
protected Expression	simplifyArguments(StaticContext env) Simplify the arguments of the function.
java.lang.String	toShortString() Produce a short string identifying the expression for use in error messages
java.lang.String	toString() The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Type-check the expression.

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

addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeCardinality, computeDependencies, computeSpecialProperties, computeStaticProperties, copy, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getConstructType, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getItemType, getLocalRetainedStaticContext, getLocation, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getStreamerName, hasCompatibleStaticContext, hashCode, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isCallOnSystemFunction, isIdentical, isInstruction, isLiftable, isMultiThreaded, isSameExpression, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, typeCheckChildren, typeError, unordered, verifyParentPointers, verifyParentPointers

Methods inherited from class java.lang.Object

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

Constructor Detail

FunctionCall

public FunctionCall()

Method Detail

setOperanda

protected void setOperanda(OperandArray operanda)

Set the data structure for the operands of this expression. This must be created during initialisation of the expression and must not be subsequently changed

Parameters:

operanda - the data structure for expression operands

getOperanda

public OperandArray getOperanda()

Get the data structure holding the operands of this expression.

Returns:

the data structure holding expression operands

operands

public java.lang.Iterable<Operand> operands()

Description copied from class: Expression

Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression. Default implementation works off the results of iterateSubExpressions()

If the expression is a Callable, then it is required that the order of the operands returned by this function is the same as the order of arguments supplied to the corresponding call() method.

Overrides:

operands in class Expression

Returns:

an iterator containing the sub-expressions of this expression

getTargetFunction

public abstract Function getTargetFunction(XPathContext context)
                                    throws XPathException

Get the target function to be called

Parameters:

context - the dynamic evaluation context

Returns:

the target function

Throws:

XPathException - if the target function cannot be determined

getFunctionName

public abstract StructuredQName getFunctionName()

Get the qualified of the function being called

Returns:

the qualified name. May be null if the function is anonymous.

getArity

public final int getArity()

Determine the number of actual arguments supplied in the function call

Returns:

the arity (the number of arguments)

setArguments

public void setArguments(Expression[] args)

Method called by the expression parser when all arguments have been supplied

Parameters:

args - the expressions contained in the argument list of the function call

setOperanda

protected void setOperanda(Expression[] args,
                           OperandRole[] roles)

getArguments

public Expression[] getArguments()

Get the expressions supplied as actual arguments to the function

Returns:

the array of expressions supplied in the argument list of the function call. The array is newly constructed to ensure that modifications to the array have no effect.

getArg

public Expression getArg(int n)

Get the expression supplied as the Nth argument

Parameters:

n - the required argument, zero-based

Returns:

the expression supplied in the relevant position

Throws:

java.lang.IllegalArgumentException - if the value of n is out of range

setArg

public void setArg(int n,
                   Expression child)

Set the expression to be used as the Nth argument

Parameters:

n - the required argument, zero-based

child - the expression to be used in the relevant position

Throws:

java.lang.IllegalArgumentException - if the value of n is out of range

simplifyArguments

protected final Expression simplifyArguments(StaticContext env)
                                      throws XPathException

Simplify the arguments of the function. Called from the simplify() method of each function.

Parameters:

env - the static context

Returns:

the result of simplifying the arguments of the expression

Throws:

XPathException - if an error occurs

typeCheck

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

Type-check the expression. This also calls preEvaluate() to evaluate the function if all the arguments are constant; functions that do not require this behavior can override the preEvaluate method.

Overrides:

typeCheck in class Expression

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:

the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations

Throws:

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

preEvaluateIfConstant

protected Expression preEvaluateIfConstant(ExpressionVisitor visitor)
                                    throws XPathException

Throws:

XPathException

checkFunctionCall

public void checkFunctionCall(Function target,
                              ExpressionVisitor visitor)
                       throws XPathException

Check the function call against the declared function signature, applying the function conversion rules to each argument as necessary

Parameters:

target - the function being called

visitor - an expression visitor

Throws:

XPathException - if there is a type error

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ContextItemStaticInfo contextItemType)
                    throws XPathException

Perform optimisation of an expression and its subexpressions.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

Overrides:

optimize in class Expression

Parameters:

visitor - an expression visitor

contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE

Returns:

the original expression, rewritten if appropriate to optimize execution

Throws:

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

getNetCost

public int getNetCost()

Return the estimated cost of evaluating an expression. This is a very crude measure based on the syntactic form of the expression (we have no knowledge of data values). We take the cost of evaluating a simple scalar comparison or arithmetic expression as 1 (one), and we assume that a sequence has length 5. The resulting estimates may be used, for example, to reorder the predicates in a filter expression so cheaper predicates are evaluated first.

Overrides:

getNetCost in class Expression

Returns:

the intrinsic cost of this operation, excluding the costs of evaluating the operands

preEvaluate

public Expression preEvaluate(ExpressionVisitor visitor)
                       throws XPathException

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.

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

checkArguments

protected void checkArguments(ExpressionVisitor visitor)
                       throws XPathException

Method supplied by each class of function to check arguments during parsing, when all the argument expressions have been read

Parameters:

visitor - the expression visitor

Throws:

XPathException - if the arguments are incorrect

checkArgumentCount

protected int checkArgumentCount(int min,
                                 int max)
                          throws XPathException

Check number of arguments.
A convenience routine for use in subclasses.

Parameters:

min - the minimum number of arguments allowed

max - the maximum number of arguments allowed

Returns:

the actual number of arguments

Throws:

XPathException - if the number of arguments is out of range

getImplementationMethod

public int getImplementationMethod()

An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.

Specified by:

getImplementationMethod in class Expression

Returns:

the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

pluralArguments

public static java.lang.String pluralArguments(int num)

Utility routine used in constructing error messages: get the word "argument" or "arguments"

Parameters:

num - the number of arguments

Returns:

the singular or plural word

addExternalFunctionCallToPathMap

public PathMap.PathMapNodeSet addExternalFunctionCallToPathMap(PathMap pathMap,
                                                               PathMap.PathMapNodeSet pathMapNodes)

Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

Parameters:

pathMap - the PathMap to which the expression should be added

pathMapNodes - the node in the PathMap representing the focus at the point where this expression is called. Set to null if this expression appears at the top level, in which case the expression, if it is registered in the path map at all, must create a new path map root.

Returns:

the pathMapNode representing the focus established by this expression, in the case where this expression is the first operand of a path expression or filter expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

getExpressionName

public java.lang.String getExpressionName()

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

Overrides:

getExpressionName in class Expression

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 explain() output displaying the expression.

getDisplayName

public final java.lang.String getDisplayName()

Get the name of the function for display in messages

Returns:

the name of the function as a lexical QName

toString

public java.lang.String toString()

The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax

Overrides:

toString in class Expression

Returns:

a representation of the expression as a string

toShortString

public java.lang.String toShortString()

Produce a short string identifying the expression for use in error messages

Overrides:

toShortString in class Expression

Returns:

a short string, sufficient to identify 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

Specified by:

export in class Expression

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.

equals

public boolean equals(java.lang.Object o)

Determine whether two expressions are equivalent

Overrides:

equals in class java.lang.Object

computeHashCode

public int computeHashCode()

Get hashCode in support of equals() method

Overrides:

computeHashCode in class Expression

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.

Overrides:

iterate in class Expression

Parameters:

context - supplies the context for evaluation

Returns:

a SequenceIterator that can be used to iterate over the result of the expression

Throws:

XPathException - if any dynamic error occurs evaluating the expression

evaluateArguments

public Sequence[] evaluateArguments(XPathContext context)
                             throws XPathException

Throws:

XPathException

adjustRequiredType

public boolean adjustRequiredType(JavaExternalObjectType requiredType)
                           throws XPathException

When a call to a Java extension function appears in a context where there the required type is a Java external object (typically an xsl:variable with a declared type, or as an argument to another Java extension function), notify this required type so that the process of converting the result to an XDM value can be short-circuited.

Parameters:

requiredType - the required type of the result of the function, determined by the context in which the function call appears

Returns:

Ok if the type has been successfully adjusted

Throws:

XPathException - if the required return type is incompatible with the type actually returned by the Java method