com.saxonica.hof
Class FirstClassFunction

java.lang.Object
  com.saxonica.hof.AbstractFunctionItem
      com.saxonica.hof.FirstClassFunction

All Implemented Interfaces:

Serializable, PullEvent, FunctionItem, Item, ValueRepresentation

public class FirstClassFunction
extends AbstractFunctionItem

A FirstClassFunction is a value that encapsulates a function; it can therefore be manipulated like any other value: for example it can be assigned to a variable and passed as a parameter to a function.

A FirstClassFunction can be created using the extension function saxon:function(), and can be invoked using the extension function saxon:call().

In XQuery 1.1, a FirstClassFunction can be created using an inline function literal (for example "fn:contains#2" or an inline function definition, for example "function($x) {$x=0}". It can be called using a dynamic function call such as $f(17).

Currently all FirstClassFunction objects are created statically (at compile time).

See Also:

Serialized Form

Field Summary

Fields inherited from interface net.sf.saxon.om.ValueRepresentation

EMPTY_VALUE_ARRAY

Constructor Summary

protected

FirstClassFunction(Expression target, StructuredQName name, int arity, FunctionItemType type)

Method Summary

int	getArity() Get the arity of the function
FunctionItemType	getFunctionItemType() Determine the item type of the items in the value
StructuredQName	getFunctionName() Get the name of the function
ValueRepresentation	invoke(ValueRepresentation[] args, XPathContext context) Invoke the function
void	typeCheck(ExpressionVisitor visitor, ItemType contextItemType) Type check the function (may modify it by adding code for converting the arguments)

Methods inherited from class com.saxonica.hof.AbstractFunctionItem

bind, curry, explain, getStringValue, getStringValueCS, getTypedValue, optimize

Methods inherited from class java.lang.Object

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

Constructor Detail

FirstClassFunction

protected FirstClassFunction(Expression target,
                             StructuredQName name,
                             int arity,
                             FunctionItemType type)

Method Detail

getArity

public int getArity()

Get the arity of the function

Returns:

the number of arguments

getFunctionName

public StructuredQName getFunctionName()

Get the name of the function

Returns:

the name of the function, if it has a name, or null otherwise

getFunctionItemType

public FunctionItemType getFunctionItemType()

Determine the item type of the items in the value

Returns:

the function item type

typeCheck

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

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

Overrides:

typeCheck in class AbstractFunctionItem

Parameters:

visitor - the expression visitor, supplies context information

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

Throws:

XPathException

invoke

public ValueRepresentation invoke(ValueRepresentation[] args,
                                  XPathContext context)
                           throws XPathException

Invoke the function

Parameters:

args - the actual arguments to be supplied

context - the XPath dynamic evaluation context

Returns:

the result of invoking the function

Throws:

XPathException