Add list:intersperse list:at list:unique list:sort

2 files changed, 97 insertions, 2 deletions

diff --git a/gen/src/list.erl b/gen/src/list.erl
index 39a30a3..10a093a 100644
--- a/gen/src/list.erl
+++ b/gen/src/list.erl
@@ -1,7 +1,7 @@
 -module(list).
 -compile(no_auto_import).
 
--export([length/1, reverse/1, is_empty/1, contains/2, head/1, tail/1, filter/2, map/2, traverse/2, drop/2, take/2, new/0, append/2, flatten/1, fold/3, fold_right/3, find/2, all/2, any/2, zip/2]).
+-export([length/1, reverse/1, is_empty/1, contains/2, head/1, tail/1, filter/2, map/2, traverse/2, drop/2, take/2, new/0, append/2, flatten/1, fold/3, fold_right/3, find/2, all/2, any/2, zip/2, intersperse/2, at/2, unique/1, sort/1]).
 
 length(A) ->
     erlang:length(A).
@@ -213,3 +213,76 @@ zip(L1, L2) ->
         {[X1 | Rest1], [X2 | Rest2]} ->
             [{X1, X2} | zip(Rest1, Rest2)]
     end.
+
+intersperse(List, Elem) ->
+    case List of
+        [] ->
+            [];
+
+        [X] ->
+            [X];
+
+        [X1 | Rest] ->
+            [X1, Elem | intersperse(Rest, Elem)]
+    end.
+
+at(List, I) ->
+    case I < 0 of
+        true ->
+            {error, not_found};
+
+        false ->
+            case List of
+                [] ->
+                    {error, not_found};
+
+                [X | Rest] ->
+                    case I =:= 0 of
+                        true ->
+                            {ok, X};
+
+                        false ->
+                            at(Rest, I - 1)
+                    end
+            end
+    end.
+
+unique(List) ->
+    case List of
+        [] ->
+            [];
+
+        [X | Rest] ->
+            [X | unique(filter(Rest, fun(Y) -> Y /= X end))]
+    end.
+
+merge_sort(A, B) ->
+    case {A, B} of
+        {[], _} ->
+            B;
+
+        {_, []} ->
+            A;
+
+        {[Ax | Ar], [Bx | Br]} ->
+            case Ax < Bx of
+                true ->
+                    [Ax | merge_sort(Ar, B)];
+
+                false ->
+                    [Bx | merge_sort(A, Br)]
+            end
+    end.
+
+sort(List) ->
+    ListLength = length(List),
+    case ListLength < 2 of
+        true ->
+            List;
+
+        false ->
+            SplitLength = ListLength div 2,
+            AList = take(List, SplitLength),
+            BList = drop(List, SplitLength),
+            merge_sort(sort(AList), sort(BList))
+    end.
diff --git a/gen/test/list_test.erl b/gen/test/list_test.erl
index 9cb1ac3..6105a88 100644
--- a/gen/test/list_test.erl
+++ b/gen/test/list_test.erl
@@ -1,7 +1,7 @@
 -module(list_test).
 -compile(no_auto_import).
 
--export([length_test/0, reverse_test/0, is_empty_test/0, contains_test/0, head_test/0, tail_test/0, filter_test/0, map_test/0, traverse_test/0, drop_test/0, take_test/0, new_test/0, append_test/0, flatten_test/0, fold_test/0, fold_right_test/0, find_test/0, all_test/0, any_test/0, zip_test/0]).
+-export([length_test/0, reverse_test/0, is_empty_test/0, contains_test/0, head_test/0, tail_test/0, filter_test/0, map_test/0, traverse_test/0, drop_test/0, take_test/0, new_test/0, append_test/0, flatten_test/0, fold_test/0, fold_right_test/0, find_test/0, all_test/0, any_test/0, zip_test/0, intersperse_test/0, at_test/0, unique_test/0, sort_test/0]).
 
 length_test() ->
     expect:equal(list:length([]), 0),
@@ -110,3 +110,25 @@ zip_test() ->
     expect:equal(list:zip([1, 2, 3], [4, 5, 6]), [{1, 4}, {2, 5}, {3, 6}]),
     expect:equal(list:zip([5, 6], [1, 2, 3]), [{5, 1}, {6, 2}]),
     expect:equal(list:zip([5, 6, 7], [1, 2]), [{5, 1}, {6, 2}]).
+
+intersperse_test() ->
+    expect:equal(list:intersperse([1, 2, 3], 4), [1, 4, 2, 4, 3]),
+    expect:equal(list:intersperse([], 2), []).
+
+at_test() ->
+    expect:equal(list:at([1, 2, 3], 2), {ok, 3}),
+    expect:is_error(list:at([1, 2, 3], 5)),
+    expect:is_error(list:at([], 0)),
+    expect:is_error(list:at([1, 2, 3, 4, 5, 6], -1)).
+
+unique_test() ->
+    expect:equal(list:unique([1, 1, 2, 3, 4, 4, 4, 5, 6]), [1, 2, 3, 4, 5, 6]),
+    expect:equal(list:unique([7, 1, 45, 6, 2, 47, 2, 7, 5]),
+                 [7, 1, 45, 6, 2, 47, 5]),
+    expect:equal(list:unique([3, 4, 5]), [3, 4, 5]),
+    expect:equal(list:unique([]), []).
+
+sort_test() ->
+    expect:equal(list:sort([4, 3, 6, 5, 4]), [3, 4, 4, 5, 6]),
+    expect:equal(list:sort([]), []),
+    expect:equal(list:sort([{1, 2}, {4, 5}, {3, 2}]), [{1, 2}, {3, 2}, {4, 5}]).