Data commit

Task/First-class-environments/Erlang/first-class-environments.erl

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+-module( first_class_environments ).
+
+-export( [task/0] ).
+
+task() ->
+	Print_pid = erlang:spawn( fun() -> print_loop() end ),
+	Environments = lists:seq( 1, 12 ),
+	Print_pid ! "Environment:   Sequence",
+	Pids = [erlang:spawn(fun() -> hailstone_in_environment(Print_pid, X) end) || X <- Environments],
+	Counts = counts( Pids ),
+	Print_pid ! "{Environment, Step count}",
+	Print_pid ! lists:flatten( io_lib:format("~p", [Counts]) ),
+	ok.
+
+
+
+counts( Pids ) ->
+	My_pid = erlang:self(),
+	[X ! {count, My_pid} || X <- Pids],
+	counts( Pids, [] ).
+	
+counts( [], Acc ) -> Acc;
+counts( Pids, Acc ) ->
+	receive
+	{count, N, Count, Pid} -> counts( lists:delete(Pid, Pids), [{N, Count} | Acc] )
+	end.
+
+hailstone_in_environment( Print_pid, N ) ->
+	erlang:put( hailstone_value, N ),
+	erlang:put( count, 0 ),
+	hailstone_loop( hailstone_loop_done(N), Print_pid, N, [N] ).
+
+hailstone_loop( stop, Print_pid, N, Acc ) ->
+	Environment = lists:flatten( io_lib:format("~11B:", [N]) ),
+	Sequence = lists:flatten( [io_lib:format("~4B", [X]) || X <- lists:reverse(Acc)] ),
+	Print_pid ! Environment ++ Sequence,
+	Count= erlang:get( count ),
+	receive
+	{count, Pid} -> Pid ! {count, N, Count, erlang:self()}
+	end;
+hailstone_loop( keep_going, Print_pid, N, Acc ) ->
+	Next = hailstone_next( erlang:get(hailstone_value) ),
+	erlang:put( hailstone_value, Next ),
+	Count = erlang:get( count ),
+	erlang:put( count, Count + 1 ),
+	hailstone_loop( hailstone_loop_done(Next), Print_pid, N, [Next | Acc]  ).
+
+hailstone_loop_done( 1 ) -> stop;
+hailstone_loop_done( _N ) -> keep_going.
+
+hailstone_next( 1 ) -> 1;
+hailstone_next( Even ) when (Even rem 2) =:= 0 -> Even div 2;
+hailstone_next( Odd ) -> (3 * Odd) + 1.
+
+print_loop() ->
+	receive
+	String -> io:fwrite("~s~n", [String] )
+	end,
+	print_loop().