Module inherittance in Erlang

Erlang support module inheritance via extends module property.

Here is the example code:

parent.erl
-------------

-module (parent).
-export( [fun1/0, fun2/0] ).

fun1() ->
io:format( "In parent::fun1/0~n" ).

fun2() ->
io:format( "In parent:fun2/0~n" ).


child.erl
----------

-module (child).
-extends(parent).
-export( [fun1/0] ).

fun1() ->
io:format( "In child:fun1/0~n" ).


Testing this:

erl

> c(parent), c(child).
{ok,child}.
> parent:fun1().
In parent:fun1/0
> parent:fun2().
In parent:fun2/0.
> child:fun1().
In child:fun1/0.
> child:fun2().
In parent:fun2/0

Even though fun2 is not defined/exported in child module, calling child:fun2/0 is a valid call as parent has exported fun2/0 function.

If you call module_info() on child, you won't see fun2 function in the exported function list. Erlang VM find the extended module via attributes property of the module.