Package net.sf.saxon.functions

Interface FunctionLibrary

    • Method Detail

      • setConfiguration

        default void setConfiguration​(Configuration config)
        Supply details of the configuration in use.
        Parameters:
        config - the configuration. The default implementation does nothing (many function libraries do not need to know any configuration details)

      • isAvailable

        boolean isAvailable​(SymbolicName.F functionName,
                    int languageLevel)
        Test whether a function with a given name and arity is available

        This supports the function-available() function in XSLT.

        Parameters:
        functionName - the qualified name of the function being called, together with its arity. For legacy reasons, the arity may be set to -1 to mean any arity will do
        languageLevel - the XPath language level (times 10, e.g. 31 for XPath 3.1)
        Returns:
        true if a function of this name and arity is available for calling

      • bind

        Expression bind​(SymbolicName.F functionName,
                Expression[] staticArgs,
                java.util.Map<StructuredQName,​java.lang.Integer> keywords,
                StaticContext env,
                java.util.List<java.lang.String> reasons)
         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.
        Parameters:
        functionName - the QName of the function being called
        staticArgs - Contains the expressions supplied statically in arguments to 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. 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).

        keywords - May be null if no keywords are used in the function call. Otherwise, a map identifying the keywords appearing in the function call, and the 0-based position at which they appeared.
        env - The static context of the function call
        reasons - If no matching function is found by the function library, it may add a diagnostic explanation to this list explaining why none of the available functions could be used.
        Returns:
        An expression equivalent to a call on the specified function, if one is found; null if no function was found matching the required name and arity.
        Throws:
        XPathException - if a matching function was identified, but the call is incorrect, for example because it uses incorrect argument keywords

      • copy

        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.
        Returns:
        a copy of this function library. This must be an instance of the original class.

      • getFunctionItem

        FunctionItem getFunctionItem​(SymbolicName.F functionName,
                             StaticContext staticContext)
                      throws XPathException
        Test whether a function with a given name and arity is available; if so, return a function item that can be dynamically called.

        This supports the function-lookup() function in XPath 3.0.

        Parameters:
        functionName - the qualified name of the function being called
        staticContext - the static context to be used by the function, in the event that it is a system function with dependencies on the static context
        Returns:
        if a function of this name and arity is available for calling, then a corresponding function item; or null if the function does not exist
        Throws:
        XPathException - in the event of certain errors, for example attempting to get a function that is private