[erlang-questions] Recommendations on optional callbacks

[Jay Nelson]

We have created a behaviour with -callbacks, but would like to simplify
the implementation by providing default implementations of some of the
callbacks. Using erlang:function_exported/3 to test for a user-supplied
callback and instead calling a default implementation may work, but the
compiler will complain for the user-defined module if no callback is
supplied. What is the recommended best practice for this situation?
The best I can come up with is to document the default implementation
and leave it up to the user-defined module to call that function or
provide its own so that the callback is always present.

jay