-export(
[ unique_preserve_order/1
+ , map_rev/2
]).
[A].
+%% @doc O(N), tail-recursive equivalent to lists:rev(lists:map(F, L))
+%% @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) ->
-export(
[ t_unique_preserve_order/1
, t_hope_list_specs/1
+ , t_map_rev/1
]).
Tests =
[ t_unique_preserve_order
, t_hope_list_specs
+ , t_map_rev
],
Properties = [parallel],
[{?GROUP, Properties, Tests}].
%% Test cases
%% =============================================================================
+t_map_rev(_Cfg) ->
+ F = fun (N) -> N + 1 end,
+ [4, 3, 2] = hope_list:map_rev([1, 2, 3], F),
+ [] = hope_list:map_rev([], F).
+
t_unique_preserve_order(_Cfg) ->
?PROPTEST(prop_unique_preserve_order).