-export(
[ unique_preserve_order/1
+ , map/2
+ , map/3 % Tunable recursion limit
+ , map_rev/2
+ , map_slow/2
+ , first_match/2
]).
+-define(DEFAULT_RECURSION_LIMIT, 1000).
+
+
-type t(A) ::
[A].
+%% @doc Tail-recursive equivalent of lists:map/2
+%% @end
+-spec map([A], fun((A) -> (B))) ->
+ [B].
+map(Xs, F) ->
+ map(Xs, F, ?DEFAULT_RECURSION_LIMIT).
+
+-spec map([A], fun((A) -> (B)), RecursionLimit :: non_neg_integer()) ->
+ [B].
+map(Xs, F, RecursionLimit) ->
+ map(Xs, F, RecursionLimit, 0).
+
+map([], _, _, _) ->
+ [];
+map([X1], F, _, _) ->
+ Y1 = F(X1),
+ [Y1];
+map([X1, X2], F, _, _) ->
+ Y1 = F(X1),
+ Y2 = F(X2),
+ [Y1, Y2];
+map([X1, X2, X3], F, _, _) ->
+ Y1 = F(X1),
+ Y2 = F(X2),
+ Y3 = F(X3),
+ [Y1, Y2, Y3];
+map([X1, X2, X3, X4], F, _, _) ->
+ Y1 = F(X1),
+ Y2 = F(X2),
+ Y3 = F(X3),
+ Y4 = F(X4),
+ [Y1, Y2, Y3, Y4];
+map([X1, X2, X3, X4, X5 | Xs], F, RecursionLimit, RecursionCount) ->
+ Y1 = F(X1),
+ Y2 = F(X2),
+ Y3 = F(X3),
+ Y4 = F(X4),
+ Y5 = F(X5),
+ Ys =
+ case RecursionCount > RecursionLimit
+ of true -> map_slow(Xs, F)
+ ; false -> map (Xs, F, RecursionLimit, RecursionCount + 1)
+ end,
+ [Y1, Y2, Y3, Y4, Y5 | Ys].
+
+
+%% @doc lists:reverse(map_rev(L, F))
+%% @end
+-spec map_slow([A], fun((A) -> (B))) ->
+ [B].
+map_slow(Xs, F) ->
+ lists:reverse(map_rev(Xs, F)).
+
+
+%% @doc Tail-recursive alternative to lists:map/2, which accumulates and
+%% returns list in reverse order.
+%% @end
+-spec map_rev([A], fun((A) -> (B))) ->
+ [B].
+map_rev(Xs, F) ->
+ map_rev_acc(Xs, F, []).
+
+-spec map_rev_acc([A], fun((A) -> (B)), [B]) ->
+ [B].
+map_rev_acc([], _, Ys) ->
+ Ys;
+map_rev_acc([X|Xs], F, Ys) ->
+ Y = F(X),
+ map_rev_acc(Xs, F, [Y|Ys]).
+
+
-spec unique_preserve_order(t(A)) ->
t(A).
unique_preserve_order(L) ->
end
end,
lists:reverse(lists:foldl(PrependIfNew, [], L)).
+
+-spec first_match([{Tag, fun((A) -> boolean())}], A) ->
+ hope_option:t(Tag).
+first_match([], _) ->
+ none;
+first_match([{Tag, F} | Tests], X) ->
+ case F(X)
+ of true -> {some, Tag}
+ ; false -> first_match(Tests, X)
+ end.