spawn and send in Erlang

A process is cheap; ! sends, receive waits for a match.

%% A process is cheap; ! sends, receive waits for a match.
operator() ->
    receive
        {connect, From, Line} ->
            From ! {ok, Line},
            operator();
        hang_up ->
            ok
    end.

main(_) ->
    Pid = spawn(fun operator/0),
    Pid ! {connect, self(), 7},
    receive
        {ok, Line} -> io:format("Patched through line ~p~n", [Line])
    end,
    Pid ! hang_up,
    io:format("Board closed~n").

How it works

1. spawn(fun operator/0) starts a process and answers its pid.
2. Pid ! Message is fire-and-forget; self() names the sender.
3. The operator loops by calling itself after each message.

Keywords and builtins used here

• end
• format
• fun
• main
• operator
• receive
• spawn

The run, in numbers

Lines

18

Characters to type

342

Tokens

100

Three-star pace

60 tpm

At the three-star pace of 60 tokens a minute, this run takes about 100 seconds.

Type this snippet

Step 1 of 4 in Processes, step 25 of 31 in Language basics.

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