Proplists in Erlang

Tagged tuples in a list: the classic options style.

%% Proplists: tagged tuples in a list, the classic options style.
main(_) ->
    Options = [{speed, 300}, {parity, even}, duplex],

    io:format("Speed: ~p~n", [proplists:get_value(speed, Options)]),
    io:format("Stop bits: ~p~n",
              [proplists:get_value(stop_bits, Options, 1)]),
    io:format("Duplex? ~p~n", [proplists:get_bool(duplex, Options)]),

    %% lists:keyfind works on any tagged-tuple list.
    case lists:keyfind(parity, 1, Options) of
        {parity, P} -> io:format("Parity ~p~n", [P]);
        false -> io:format("No parity set~n")
    end.

How it works

1. proplists:get_value reads with an optional default.
2. A bare atom like duplex means {duplex, true}.
3. lists:keyfind searches any tagged-tuple list by position.

Keywords and builtins used here

• case
• end
• format
• get_bool
• get_value
• keyfind
• main
• of

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Step 3 of 4 in Data shapes, step 17 of 31 in Language basics.

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