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## net.sf.saxon.functions
Class ExecutableFunctionLibrary

    java.lang.Object
      net.sf.saxon.functions.ExecutableFunctionLibrary

All Implemented Interfaces:
  Serializable, FunctionLibrary

    public class ExecutableFunctionLibrary

extends Object
implements FunctionLibrary

An ExecutableFunctionLibrary is a function library that contains definitions of functions for use at run-time. Normally functions are bound at compile-time; however there are various situations in which the information is needed dynamically, for example (a) to support the XSLT function-available() call (in the pathological case where the argument is not known statically), (b) to allow functions to be called from saxon:evaluate(), (c) to allow functions to be called from a debugging breakpoint. The objects actually held in the ExecutableFunctionLibrary are UserFunctionCall objects that have been prepared at compile time. These are function calls that do full dynamic type checking: that is, they are prepared on the basis that the static types of the arguments are all "item()*", meaning that full type checking is needed at run-time.

See Also:
  Serialized Form

Constructor Summary
`ExecutableFunctionLibrary(Configuration config)`

Method Summary
`void` | `addFunction(UserFunction fn)` Register a function with the function library
`Expression` | `bind(int nameCode, String uri, String local, Expression[] staticArgs)` Bind a function, given the URI and local parts of the function name, and the list of expressions supplied as arguments.
`FunctionLibrary` | `copy()` This method creates a copy of a FunctionLibrary: if the original FunctionLibrary allows new functions to be added, then additions to this copy will not affect the original, or vice versa.
`boolean` | `isAvailable(int fingerprint, String uri, String local, int arity)` Test whether a function with a given name and arity is available.

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### ExecutableFunctionLibrary

    public ExecutableFunctionLibrary(Configuration config)

Method Detail

### addFunction

    public void addFunction(UserFunction fn)

  Register a function with the function library

### isAvailable

    public boolean isAvailable(int fingerprint,
                               String uri,
                               String local,
                               int arity)

  Test whether a function with a given name and arity is available. This supports the function-available() function in XSLT.

  Specified by:
    `isAvailable` in interface `FunctionLibrary`
  Parameters:
    `uri` - The URI of the function name
    `local` - The local part of the function name
    `arity` - The number of arguments. This is set to -1 in the case of the single-argument function-available() function; in this case the method should return true if there is some matching extension function, regardless of its arity.
    `fingerprint` - The namepool fingerprint of the function name. This must match the uri and localName; the information is provided redundantly to avoid repeated lookups in the name pool.

### bind

    public Expression bind(int nameCode,
                           String uri,
                           String local,
                           Expression[] staticArgs)
                    throws XPathException

  Bind a function, given the URI and local parts of the function name, and the list of expressions supplied as arguments. This method is called at compile time.

  Specified by:
    `bind` in interface `FunctionLibrary`
  Parameters:
    `nameCode` - The namepool nameCode of the function name. The uri and local name are also supplied (redundantly) to avoid fetching them from the name pool.
    `uri` - The URI of the function name
    `local` - The local part of the function name
    `staticArgs` - The expressions supplied statically in the function call. The intention is that the static type of the arguments (obtainable via getItemType() and getCardinality() may be used as part of the binding algorithm.
  Returns:
    An object representing the extension function to be called, if one is found; null if no extension function was found matching the required name and arity.
  Throws:
    `XPathException` - if a function is found with the required name and arity, but the implementation of the function cannot be loaded or used; or if an error occurs while searching for the function; or if this function library "owns" the namespace containing the function call, but no function was found.

### copy

    public FunctionLibrary copy()

  This method creates a copy of a FunctionLibrary: if the original FunctionLibrary allows new functions to be added, then additions to this copy will not affect the original, or vice versa.

  Specified by:
    `copy` in interface `FunctionLibrary`
  Returns:
    a copy of this function library. This must be an instance of the original class.

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Copyright (C) Michael H. Kay. All rights reserved.