core.erl

-module(core).
-export([front_end_task/0, task/1, main/1]).

%% Call fn                                                                                                                                                  
%% Get back a future                                                                                                                                        
%% Dereference                                                                                                                                              
%%  - Blocks until if not done, then returns                                                                                                                
%%  - If done, returns immediately                                                                                                                          

task(Pid) ->
    %% Maybe querying a database or something. This takes a while.                                                                                          
    timer:sleep(3000),
    Pid ! 5. %%% 5 is the result of this ficticous computation.                                                                                             

front_end_task() ->
    spawn(core, task, [self()]),
    fun() ->
            receive Result ->
                    Result
            end
    end.

main(_) ->
    io:format("Calling the front-end task...~n"),
    Future = front_end_task(),
    io:format("Got a future back. Returned immediately. Dereferencing the future...~n"),
    io:format("Dereferencing returned ~w.~n", [Future()]),
    io:format("Result has been returned.~n").                                                                                                               

%% Sample run:                                                                                                                                              
%% mike@nadia ~/projects/erlang-futures $ escript core.erl                                                                                                  
%% Calling the front-end task...                                                                                                                            
%% Got a future back. Returned immediately. Dereferencing the future...                                                                                     
%% <Bit of a wait here>                                                                                                                                     
%% Dereferencing returned 5.                                                                                                                                
%% Result has been returned.