Erlang/OTP Forums

AB = [[lists:nth(X, A),lists:nth(X,B)] || X <- lists:seq(1, length(A))].

[tuple_to_list(E) || E <- lists:zip([1,2,3], [4,5,6])]

-module(benchmarks_are_fun).
-export([test/1, loop/2]).
-define(A, [1,2,3]).
-define(B, [4,5,6]).
-define(Control, [[1,4],[2,5],[3,6]]).

map_zip(A, B) ->
    lists:map(fun({X,Y}) -> [X,Y] end, lists:zip(A,B)).

lc1(A, B) ->
    [[X,Y] || {X,Y} <- lists:zip(A,B)].

lc2(A, B) ->
    [tuple_to_list(X) || X <- lists:zip(A,B)].
   
lc3(A, B) ->
    [[lists:nth(X, A),lists:nth(X, B)] || X <- lists:seq(1, length(A))].

manual([Ha|Ta], [Hb|Tb]) ->
    manual(Ta, Tb, [[Ha,Hb]]).

manual([Ha|Ta], [Hb|Tb], Acc) ->
    manual(Ta, Tb, Acc ++ [[Ha,Hb]]);
manual([], [], Acc) ->
    Acc.

loop(0, Fun) ->
    Fun(?A, ?B);
loop(N, Fun) ->
    Fun(?A, ?B),
    loop(N - 1, Fun).

test(N) ->
    {Time1, Control} = timer:tc(benchmarks_are_fun, loop, [N, fun map_zip/2]),
    {Time2, Control} = timer:tc(benchmarks_are_fun, loop, [N, fun lc1/2]),
    {Time3, Control} = timer:tc(benchmarks_are_fun, loop, [N, fun lc2/2]),
    {Time4, Control} = timer:tc(benchmarks_are_fun, loop, [N, fun lc3/2]),
    {Time5, Control} = timer:tc(benchmarks_are_fun, loop, [N, fun manual/2]),
    {{map_zip, Time1},
     {list_comprehension_zip_and_pattern_matching, Time2},
     {list_comprehension_zip_tuple_to_list, Time3},
     {list_comprehension_nth, Time4},
     {manual_recursive, Time5}}.

1> m(lists).
Module lists compiled: Date: May 28 2006, Time: 08.51
Compiler options:  [{cwd,"/builddir/build/BUILD/otp_src_R11B-0/lib/stdlib/src"},
                    {outdir,"/builddir/build/BUILD/otp_src_R11B-0/lib/stdlib/src/../ebin"},
                    {i,"/builddir/build/BUILD/otp_src_R11B-0/lib/stdlib/src/../include"},
                    {i,"/builddir/build/BUILD/otp_src_R11B-0/lib/stdlib/src/../../kernel/include"},
                    strict_record_tests,
                    debug_info]
Object file: /usr/lib/erlang/lib/stdlib-1.14/ebin/lists.beam
Exports:
all/2                         min/1
all/3                         module_info/0
any/2                         module_info/1
any/3                         nth/2
append/2                      nthtail/2
append/1                      partition/2
concat/1                      prefix/2
...

3> lists:module_info(attributes).
[{vsn,[6968511119412774106372288869712845437]},
 {deprecated,[{keymap,4},
              {all,3},
              {any,3},
              {map,3},
              {flatmap,3},
              {foldl,4},
              {foldr,4},
              {filter,3},
              {mapfoldl,4},
              {mapfoldr,4},
              {foreach,3}]}]