Title here
Summary here
Enums in Erlang
Our enum type ServerState has an underlying int type.
-type server_state() :: state_idle | state_connected | state_error | state_retrying.
-define(STATES, [state_idle, state_connected, state_error, state_retrying]).
-module(enums).
-export([main/0, transition/1, server_state_string/1]).
%% Define the possible states
-define(STATE_STR, #{state_idle => "idle",
state_connected => "connected",
state_error => "error",
state_retrying => "retrying"}).
%% Define the main function
main() ->
Ns = transition(state_idle),
io:format("~s~n", [server_state_string(Ns)]),
Ns2 = transition(Ns),
io:format("~s~n", [server_state_string(Ns2)]).
%% Function to handle state transitions
transition(State) ->
case State of
state_idle ->
state_connected;
state_connected ->
state_idle;
state_retrying ->
state_idle;
state_error ->
state_error;
_ ->
erlang:error({unknown_state, State})
end.
%% Function to return the string representation of a state
server_state_string(State) ->
maps:get(State, ?STATE_STR).To run the program, save the code in a file named enums.erl and then use the Erlang shell to compile and run it.
$ erlc enums.erl
$ erl -noshell -s enums main -s init stop
connected
idleThe transition function emulates a state transition for a server; it takes the existing state and returns a new state. The server_state_string function returns the string representation of each state, enabling us to print the current state in a human-readable format.