[erlang-questions] Proposal: Addition to lists module - shuffle/randomize list

Andreas Hillqvist <>
Thu Jan 31 17:28:53 CET 2008


Thank you for your feedback. I had missed those. ;-)


Regards
Andreas Hillqvist

2008/1/31, t ty <>:
> Hello,
>
> See also
>
> http://www.erlang.org/pipermail/erlang-questions/2007-June/027158.html
>
> and
>
> http://www.erlang.org/pipermail/erlang-patches/2007-June/000180.html
>
> for previous work.
>
> t
>
> On Jan 31, 2008 10:30 AM, Andreas Hillqvist <> wrote:
> > Is their any interest of a shuffle/randomize function in the list module?
> >
> > Something like:
> >     shuffle(List0) ->
> >         List1 = [{random:uniform(), X} || X <- List0],
> >         List2 = lists:keysort(1, List1),
> >         [X || {_, X} <- List2].
> >
> > And:
> >     shuffle(List0, Fun, Seed0) ->
> >         {List1, Seed1} = random_key(List0, Fun, Seed0, []),
> >         List2 = lists:keysort(1, List1),
> >         {[X || {_, X} <- List2], Seed1}.
> >
> >     random_key([], _Fun, Seed0, Acc) ->
> >         {Acc, Seed0};
> >     random_key([X | List], Fun, Seed0, Acc) ->
> >         {Random, Seed1} = Fun(Seed0),
> >     random_key(List, Fun, Seed1, [{Random, X} | Acc]).
> >
> > And would be called like:
> >     > lists:shuffle([1,2,3,4,5,6,7,8,9,19]).
> >     [1,6,2,19,5,7,9,3,8,4]
> >
> >     > shuffle_list:shuffle([1,2,3,4,5,6,7,8,9,19], fun
> > random:uniform_s/1, random:seed()).
> >     {[19,2,5,3,7,9,8,6,1,4],{28186,30068,19371}}
> >
> > I do not believe that it is a "must have function", just a suggestion.
> >
> > I propose a fun for the random function, to able to provide a other
> > pseudo-random number generator (PRNG) then the random module.
> > For example a cryptographically secure pseudo-random number generator (CSPRNG)
> >
> >
> > Regards
> > Andreas Hillqvist
> > _______________________________________________
> > erlang-questions mailing list
> > 
> > http://www.erlang.org/mailman/listinfo/erlang-questions
> >
>



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