Études for Erlang

Étude 7-6: Explaining an Algorithm

You need a way to shuffle the deck of cards. This is the code for doing a shuffle, taken from the Literate Programs Wiki.

shuffle(List) -> shuffle(List, []).
shuffle([], Acc) -> Acc;
shuffle(List, Acc) ->
  {Leading, [H | T]} = lists:split(random:uniform(length(List)) - 1, List),
  shuffle(Leading ++ T, [H | Acc]).

Wait a moment. If I’ve just given you the code, what’s the purpose of this étude? I want you to understand the code. The object of this étude is to write the documentation for the algorithm. If you aren’t sure what the code does, try adding some io:format statements to see what is happening. If you’re totally stuck, see the explanation from Literate Programs site.

See a suggested solution in Appendix A.