the OO metaphor

[Karlsson Mikael]

"Vlad Dumitrescu" <vladdu@REDACTED> writes:
.
.
> An example might be appropriate.
> 
> -module(base).
> 
> fun1(blip) -> foo;
> fun1(A) -> {empty, A}.
> 
> ==== and (the syntax is just a proposal)
> 
> -module(base_extended).
> -extend({base, [fun1]}).
> 
> fun1({help}) -> hohoho;
> -inherited(). %% need not be always present
> fun1(_) -> false.
.
.
> regards,
> Vlad
> 

Hi Vlad,

Without extending the erlang syntax, how about something
like?:

-module(extend_test).
-export([test1/1,test2/1]).

%% Basic framework stuff
extend_f(A,B) ->[A|B].

eval_f([H|T],A) ->
    case catch H(A) of
	{'EXIT',{function_clause,_}} -> eval_f(T,A);
	B      -> B
    end;
eval_f([],A) -> 
    empty.


%% Example
fun1(blip) -> foo.
fun2({help}) -> hohoho.

base_f() ->[fun fun2/1,fun fun1/1].

test1(A) -> eval_f(base_f(),A).

test2(A) -> 
   Extended_f = extend_f(fun(blip) -> boo end, base_f()),
   eval_f(Extended_f, A).
------
Running the example:
21> extend_test:test1(blip). 
foo
22> extend_test:test2(blip).
boo
23> extend_test:test1({help}).
hohoho
24> extend_test:test2({help}).
hohoho
25> extend_test:test2(snip).  
empty


I can understand that there are some flawns, you have to do
stuff in runtime, and naming is maybe not consistent with OO,
but maybe something to build on...

Regards
Mikael