## net.sf.saxon.query
Class XQueryFunctionLibrary

    java.lang.Object
      net.sf.saxon.query.XQueryFunctionLibrary

All Implemented Interfaces:
  Serializable, FunctionLibrary, XQueryFunctionBinder

    public class XQueryFunctionLibrary

extends Object
implements FunctionLibrary, XQueryFunctionBinder

An XQueryFunctionLibrary is a function library containing all the user-defined functions available for use within a particular XQuery module: that is, the functions declared in that module, and the functions imported from other modules. It also contains (transiently during compilation) a list of function calls within the module that have not yet been bound to a specific function declaration.

See Also:
  Serialized Form

Constructor Summary
`XQueryFunctionLibrary(Configuration config)` Create an XQueryFunctionLibrary

Method Summary
`Expression` `bind(int nameCode, String uri, String local, Expression[] arguments)` Identify a (namespace-prefixed) function appearing in the expression.
`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.
`void` `declareFunction(XQueryFunction function)` Register a user-defined XQuery function
`void` `explainGlobalFunctions(PrintStream out)` Output "explain" information about each declared function
`Configuration` `getConfiguration()` Get the Configuration options
`XQueryFunction` `getDeclaration(int nameCode, String uri, String local, Expression[] staticArgs)` Get the function declaration corresponding to a given function name and arity
`Iterator` `getFunctionDefinitions()` Get an iterator over the Functions defined in this module
`UserFunction` `getUserDefinedFunction(String uri, String localName, int arity)` Get the function with a given name and arity.
`boolean` `isAvailable(int fingerprint, String uri, String local, int arity)` Test whether a function with a given name and arity is available.
`void` `setConfiguration(Configuration config)` Set the Configuration options

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

Constructor Detail

### XQueryFunctionLibrary

    public XQueryFunctionLibrary(Configuration config)

  Create an XQueryFunctionLibrary

Method Detail

### setConfiguration

    public void setConfiguration(Configuration config)

  Set the Configuration options

### getConfiguration

    public Configuration getConfiguration()

  Get the Configuration options

### declareFunction

    public void declareFunction(XQueryFunction function)
                         throws StaticError

  Register a user-defined XQuery function

  Throws:
    `StaticError`

### 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. This method may be called either at compile time or at run time.

  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[] arguments)
                    throws XPathException

  Identify a (namespace-prefixed) function appearing in the expression. This method is called by the XQuery parser to resolve function calls found within the query.

  Note that a function call may appear earlier in the query than the definition of the function to which it is bound. Unlike XSLT, we cannot search forwards to find the function definition. Binding of function calls is therefore a two-stage process; at the time the function call is parsed, we simply register it as pending; subsequently at the end of query parsing all the pending function calls are resolved. Another consequence of this is that we cannot tell at the time a function call is parsed whether it is a call to an internal (XSLT or XQuery) function or to an extension function written in Java.

  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
    `arguments` - The expressions supplied statically in arguments to the function call. The length of this array represents the arity of the function. The intention is that the static type of the arguments (obtainable via getItemType() and getCardinality()) may be used as part of the binding algorithm. In some cases it may be possible for the function to be pre-evaluated at compile time, for example if these expressions are all constant values.

    The conventions of the XPath language demand that the results of a function depend only on the values of the expressions supplied as arguments, and not on the form of those expressions. For example, the result of f(4) is expected to be the same as f(2+2). The actual expression is supplied here to enable the binding mechanism to select the most efficient possible implementation (including compile-time pre-evaluation where appropriate).

  Returns:
    an Expression representing the function call. This will normally be a FunctionCall, but it may be rewritten as some other expression.
  Throws:
    `XPathException` - if the function call is invalid, either because it is an unprefixed call to a non-system function, or because it is calling a system function that is available in XSLT only. A prefixed function call that cannot be recognized at this stage is assumed to be a forwards reference, and is bound later when bindUnboundFunctionCalls() is called.

### getDeclaration

    public XQueryFunction getDeclaration(int nameCode,
                                         String uri,
                                         String local,
                                         Expression[] staticArgs)

  Get the function declaration corresponding to a given function name and arity

  Specified by:
    `getDeclaration` in interface `XQueryFunctionBinder`
  Returns:
    the XQueryFunction if there is one, or null if not.

### getFunctionDefinitions

    public Iterator getFunctionDefinitions()

  Get an iterator over the Functions defined in this module

  Returns:
    an Iterator, whose items are `XQueryFunction` objects. It returns all function known to this module including those imported from elsewhere; they can be distinguished by their namespace.

### explainGlobalFunctions

    public void explainGlobalFunctions(PrintStream out)
                                throws XPathException

  Output "explain" information about each declared function

  Throws:
    `XPathException`

### getUserDefinedFunction

    public UserFunction getUserDefinedFunction(String uri,
                                               String localName,
                                               int arity)

  Get the function with a given name and arity. This method is provided so that XQuery functions can be called directly from a Java application. Note that there is no type checking or conversion of arguments when this is done: the arguments must be provided in exactly the form that the function signature declares them.

  Parameters:
    `uri` - the uri of the function name
    `localName` - the local part of the function name
    `arity` - the number of arguments.

### 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.

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