@@ -5,11 +5,11 @@ -module(nglists). -export([count/2, deepmap/2, drop/2, find_first/2, find_first/3, find_last/2, find_last/3, - init/1, pos/2, transpose/1, uniq/1]). + init/1, pos/2, transpose/1, uniq/1, shuffle/1, random/1]). -import(lists, [all/2, append/1, duplicate/2, flatten/1, foldl/3, foreach/2, - map/2, nth/2, nthtail/2, reverse/1, seq/2, sum/1, zip/2, - zipwith/3]). + keysort/2, map/2, nth/2, nthtail/2, reverse/1, seq/2, sum/1, + zip/2, zipwith/3]). %%% @doc Count the number of list items that satisfy some predicate. @@ -20,9 +20,9 @@ count(Fun, L) -> %% @doc Like map, but maintains structure of deep lists. -deepmap(Fun, [H|T]) when list(H) -> [deepmap(Fun, H) | deepmap(Fun, T)]; -deepmap(Fun, [H|T]) -> [Fun(H) | deepmap(Fun,T)]; -deepmap(_Fun, []) -> []. +deepmap(Fun, [H|T]) when is_list(H) -> [deepmap(Fun, H) | deepmap(Fun, T)]; +deepmap(Fun, [H|T]) -> [Fun(H) | deepmap(Fun,T)]; +deepmap(_Fun, []) -> []. %% @doc Drop N elements from list L. @@ -74,7 +74,7 @@ pos(E, [H|_], I) when E == H -> I; pos(E, [_|T], I) -> pos(E, T, I+1). -%% @doc Transpose list L. +%% @doc Transpose list. transpose(L) -> Len = length(hd(L)), @@ -86,7 +86,23 @@ transpose1([], Acc) -> Acc. -%% @doc Remove duplicates from list L. +%% @doc Remove duplicates from list. uniq([H|T]) -> [H | uniq([Y || Y <- T, Y =/= H])]; uniq([]) -> []. + + +%% @doc Shuffle list. + +%% Knuth shuffle. +shuffle(L) -> + N = length(L) * 10000, + Pairs = map(fun(X) -> {random:uniform(N), X} end, L), + Sorted = keysort(1, Pairs), + map(fun({_, X}) -> X end, Sorted). + + +%% @doc Return an element from the list picked randomly. + +random(L) -> + nth(random:uniform(length(L)), L). \ No newline at end of file nglists.erl 675b7328ad09b7de82422105c440f23b58d71d6f Hasan Veldstra hasan.veldstra@gmail.com http://github.com/hassy/ngerl/commit/04f34b461a09406ee47a2b87f3a35b20b047a7a9 04f34b461a09406ee47a2b87f3a35b20b047a7a9 2009-06-28T06:31:16-07:00 2009-06-28T06:31:16-07:00 Add functions shuffle() and random() c71819495fbc1f8290666c1e955d9033ae3525fd Hasan Veldstra hasan.veldstra@gmail.com