Erlang/OTP Forums

%%% tvsl.erl
%%% Tuple Vs. Lists
-module(tvsl).
-export([test/1, test_list/1, test_tuple/1]).

test_list(0) ->
    ok;
test_list(N) ->
    List = [45 * 89, 48 * 95],
    [_A, _B] = List,
    test_list(N-1).

test_tuple(0) ->
    ok;
test_tuple(N) ->
    Tuple = {45 * 89, 48 * 95},
    {_A, _B} = Tuple,
    test_tuple(N-1).

test(N) ->
    {timer:tc(tvsl,test_list,[N]),
     timer:tc(tvsl,test_tuple,[N])}.

%%% tvsl2.erl
%%% Tuples vs. Lists, take 2
-module(tvsl2).
-export([test/1, sum/1, sum2/1]).

%% a few handy functions
build(list,Max)  -> lists:seq(1,Max);
build(tuple,Max) -> list_to_tuple(build(list,Max)).

sum(Z) when is_list(Z) ->
    sum_of_list(Z, 1, length(Z), 0);
sum(Z) when is_tuple(Z) ->
    sum_of_tuple(Z, 1, size(Z), 0);
sum(_) ->
    error.

%% a dead ugly way to sum up a list,
%% but similar to the way we sum up the tuple below
sum_of_list(_, Max, Max, Sum)  -> Sum + Max;
sum_of_list(Z, Curr, Max, Sum) ->
    sum_of_list(Z, Curr + 1, Max, Sum + lists:nth(Curr, Z)).

%% is there a better way to sum up (elements of) a tuple,
%% ( besides lists:sum(tuple_to_list/1) ) ?
sum_of_tuple(_, Max, Max, Sum)  -> Sum + Max;
sum_of_tuple(Z, Curr, Max, Sum) ->
    sum_of_tuple(Z, Curr + 1, Max, Sum + element(Curr, Z)).

%% a nice way to sum up a list (besides lists:sum)
sum2([H|T]) ->
    sum2(T, H).

sum2([H|T], Sum) ->
    sum2(T, H + Sum);
sum2([], Sum) ->
    Sum.

test(N) ->
    AList = build(list,N),
    ATuple = build(tuple,N),
    Control =  N * (N + 1) div 2,
    {Time1, Control} = timer:tc(tvsl2,sum2,[AList]),
    {Time2, Control} = timer:tc(tvsl2,sum,[AList]),
    {Time3, Control} = timer:tc(tvsl2,sum,[ATuple]),
    {{sum_list_ht, Time1}, {sum_list_nth, Time2}, {sum_tuple, Time3}}.