Initial data commit

Task/Singleton/Erlang/singleton-1.erl

@@ -0,0 +1,33 @@
+-module(singleton).
+
+-export([get/0, set/1, start/0]).
+
+-export([loop/1]).
+
+% spec singleton:get() -> {ok, Value::any()} | not_set
+get() ->
+     ?MODULE ! {get, self()},
+     receive
+	{ok, not_set} -> not_set;
+        Answer -> Answer
+     end.
+
+% spec singleton:set(Value::any()) -> ok
+set(Value) ->
+    ?MODULE ! {set, self(), Value},
+    receive
+        ok -> ok
+    end.
+
+start() ->
+    register(?MODULE, spawn(?MODULE, loop, [not_set])).
+
+loop(Value) ->
+    receive
+        {get, From} ->
+             From ! {ok, Value},
+             loop(Value);
+        {set, From, NewValue} ->
+             From ! ok,
+             loop(NewValue)
+        end.