functionAddress = @fn FunctionName
Returns a memory address which can be used to access the function specified by FunctionName.
FunctionName must be the name of a function which was defined or prototyped at some earlier location in the source code, in a
def fn <expr>, or
def fn <prototype> statement.
The address returned by
@fn can be used in a
def fn using statement, or as a parameter to a Toolbox function that expects the address of a callback function.
def fn using