net.sf.saxon.functions.hof

Class CoercedFunction

java.lang.Object

net.sf.saxon.functions.AbstractFunction

net.sf.saxon.functions.hof.CoercedFunction

All Implemented Interfaces:

Callable, Function, GroundedValue, Item, Sequence

public class CoercedFunction
extends AbstractFunction

A function item obtained by coercing a supplied function; this adds a wrapper to perform dynamic type checking of the arguments in any call, and type checking of the result.

Constructor Summary

Constructors

Constructor and Description
CoercedFunction(Function targetFunction, SpecificFunctionType requiredType) Create a CoercedFunction as a wrapper around a target function
CoercedFunction(SpecificFunctionType requiredType) Create a CoercedFunction whose target function is not yet known (happens during package re-loading)

Method Summary

Modifier and Type	Method and Description
Sequence	call(XPathContext context, Sequence[] args) Invoke the function
static CoercedFunction	coerce(Function suppliedFunction, SpecificFunctionType requiredType, RoleDiagnostic role) Factory method to create a CoercedFunction with a given type, for a given targetFunction.
void	export(ExpressionPresenter out) Export information about this function item to the SEF file
AnnotationList	getAnnotations() Get the function annotations.
int	getArity() Get the arity of the function
java.lang.String	getDescription() Get a description of this function for use in error messages.
FunctionItemType	getFunctionItemType() Get the item type of the function item
StructuredQName	getFunctionName() Get the name of the function, or null if it is anonymous
void	setTargetFunction(Function targetFunction) Set the target function
void	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) Type check the function (may modify it by adding code for converting the arguments)

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

atomize, deepEquals, effectiveBooleanValue, getOperandRoles, getUnicodeStringValue, isArray, isMap, isTrustedResultType, makeNewContext, simplify, toShortString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

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

getGenre, isSequenceVariadic

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

Constructor Detail

CoercedFunction

public CoercedFunction(Function targetFunction,
                       SpecificFunctionType requiredType)
                throws XPathException

Create a CoercedFunction as a wrapper around a target function

Parameters:

targetFunction - the function to be wrapped by a type-checking layer

requiredType - the type of the coerced function, that is the type required by the context in which the target function is being used

Throws:

XPathException - if the arity of the supplied function does not match the arity of the required type

CoercedFunction

public CoercedFunction(SpecificFunctionType requiredType)

Create a CoercedFunction whose target function is not yet known (happens during package re-loading)

Parameters:

requiredType - the type of the coerced function, that is the type required by the context in which the target function is being used

Method Detail

setTargetFunction

public void setTargetFunction(Function targetFunction)
                       throws XPathException

Set the target function

Parameters:

targetFunction - the function to be wrapped by a type-checking layer

Throws:

XPathException - if the arity of the supplied function does not match the arity of the required type

typeCheck

public void typeCheck(ExpressionVisitor visitor,
                      ContextItemStaticInfo contextItemType)
               throws XPathException

Type check the function (may modify it by adding code for converting the arguments)

Overrides:

typeCheck in class AbstractFunction

Parameters:

visitor - the expression visitor, supplies context information

contextItemType - the context item type at the point where the function definition appears

Throws:

XPathException - if type checking of the target function fails

getFunctionItemType

public FunctionItemType getFunctionItemType()

Get the item type of the function item

Returns:

the function item's type

getFunctionName

public StructuredQName getFunctionName()

Get the name of the function, or null if it is anonymous

Returns:

null indicating that this is an anonymous inline function

getDescription

public java.lang.String getDescription()

Get a description of this function for use in error messages. For named functions, the description is the function name (as a lexical QName). For others, it might be, for example, "inline function", or "partially-applied ends-with function".

Returns:

a description of the function for use in error messages

getArity

public int getArity()

Get the arity of the function

Returns:

the number of arguments in the function signature

getAnnotations

public AnnotationList getAnnotations()

Get the function annotations. These are the same as the annotations of the base function

Specified by:

getAnnotations in interface Function

Overrides:

getAnnotations in class AbstractFunction

Returns:

the annotations of the base function

call

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

Invoke the function

Parameters:

context - the XPath dynamic evaluation context

args - the actual arguments to be supplied

Returns:

the result of invoking the function

Throws:

XPathException - if execution of the function fails

coerce

public static CoercedFunction coerce(Function suppliedFunction,
                                     SpecificFunctionType requiredType,
                                     RoleDiagnostic role)
                              throws XPathException

Factory method to create a CoercedFunction with a given type, for a given targetFunction. It is assumed that we have already established that coercion is needed. Called from Bytecode compiler.

Parameters:

suppliedFunction - the function to be coerced

requiredType - the target type for the coercion

role - diagnostic information about the role of the expression being coerced

Returns:

the function after coercion

Throws:

XPathException - if the function cannot be coerced to the required type (for example, because it has the wrong arity)

export

public void export(ExpressionPresenter out)
            throws XPathException

Export information about this function item to the SEF file

Specified by:

export in interface Function

Overrides:

export in class AbstractFunction

Parameters:

out - the SEF output destination

Throws:

XPathException - if things go wrong