-module(fibonacci).
-export([fibonacci/0,join/1]).

fibonacci() -> 
  receive
    {Number, Customer} when Number > 1 ->
       NewCust = spawn(fibonacci,join,[Customer]),
       P = spawn(fibonacci,fibonacci,[]),
       Q = spawn(fibonacci,fibonacci,[]),
       P!{Number - 1,NewCust},
       Q!{Number - 2,NewCust};
    {Number, Customer} -> 
       Customer ! Number
  end,
  fibonacci().

join(Customer) -> receive V1 -> receive V2 -> Customer ! V1+V2 end end.

%% use, e.g., as follows:

% > c(fibonacci)

% > F = spawn(fibonacci,fibonacci,[]).

% > F ! {6,self()}.

% > flush().
% Shell got 8