Merge pull request #1548 from migmatore/add_lists_append

Add lists:append/1 and lists:append/2

These changes are made under both the "Apache 2.0" and the "GNU Lesser General
Public License 2.1 or later" license terms (dual license).

SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later

Author: bettio

CHANGELOG.md

@@ -21,6 +21,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Support to OTP-28
 - Added support for `ets:update_counter/3` and `ets:update_counter/4`.
 - Added `erlang:+/1`
+- Added `lists:append/1` and `lists:append/2`
 
 ### Fixed
 - ESP32: improved sntp sync speed from a cold boot.

libs/estdlib/src/lists.erl

@@ -4,6 +4,7 @@
 % Copyright 2017-2023 Fred Dushin <fred@dushin.net>
 % split/2 function Copyright Ericsson AB 1996-2023.
 % keytake/3 function Copyright Ericsson AB 1996-2024.
+% append/1, append/2 functions Copyright Ericsson AB 1996-2025.
 %
 % Licensed under the Apache License, Version 2.0 (the "License");
 % you may not use this file except in compliance with the License.
@@ -60,7 +61,9 @@
     split/2,
     usort/1, usort/2,
     duplicate/2,
-    sublist/2
+    sublist/2,
+    append/1,
+    append/2
 ]).
 
 %%-----------------------------------------------------------------------------
@@ -758,3 +761,36 @@ sublist(List, Len) when is_integer(Len) andalso Len >= 0 ->
 sublist0([], _Len) -> [];
 sublist0(_, 0) -> [];
 sublist0([H | Tail], Len) -> [H | sublist0(Tail, Len - 1)].
+
+%%-----------------------------------------------------------------------------
+%% @param   ListOfLists a list of lists to make the general list from
+%% @returns a list made of the sublists of `ListOfLists'.
+%% @doc     Returns a list in which all the sublists of `ListOfLists' have been appended.
+%% @end
+%%-----------------------------------------------------------------------------
+%% Attribution: https://github.com/erlang/otp/blob/34f92c2a9cbb37ef22aecf6b95613d210509015a/lib/stdlib/src/lists.erl#L222
+-spec append(ListOfLists) -> List1 when
+    ListOfLists :: [List],
+    List :: [T],
+    List1 :: [T],
+    T :: term().
+
+append([E]) -> E;
+append([H | T]) -> H ++ append(T);
+append([]) -> [].
+
+%%-----------------------------------------------------------------------------
+%% @param   List1 a list
+%% @param   List2 a list
+%% @returns a list made of the elements of `List1' and `List2'.
+%% @doc     Returns a new list `List3', which is made from the elements of `List1' followed by the elements of `List2'.
+%% @end
+%%-----------------------------------------------------------------------------
+%% Attribution: https://github.com/erlang/otp/blob/35037ba900e15bd98e778e567079b426531d0085/lib/stdlib/src/lists.erl#L202
+-spec append(List1, List2) -> List3 when
+    List1 :: [T],
+    List2 :: [T],
+    List3 :: [T],
+    T :: term().
+
+append(L1, L2) -> L1 ++ L2.

tests/libs/estdlib/test_lists.erl

@@ -2,6 +2,7 @@
 % This file is part of AtomVM.
 %
 % Copyright 2019-2021 Fred Dushin <fred@dushin.net>
+% Copyright 2025 migmatore <kazakvova201@gmail.com>
 %
 % Licensed under the Apache License, Version 2.0 (the "License");
 % you may not use this file except in compliance with the License.
@@ -49,6 +50,7 @@ test() ->
     ok = test_filtermap(),
     ok = test_last(),
     ok = test_mapfoldl(),
+    ok = test_append(),
     ok.
 
 test_nth() ->
@@ -321,4 +323,16 @@ test_mapfoldl() ->
     ?ASSERT_ERROR(lists:mapfoldl(fun(X, A) -> {X * A, A + 1} end, 1, foo), function_clause),
     ok.
 
+test_append() ->
+    ?ASSERT_MATCH(lists:append([]), []),
+    ?ASSERT_MATCH(lists:append([[1, 2, 3, 4]]), [1, 2, 3, 4]),
+    ?ASSERT_MATCH(lists:append([[1, 2], [3, 4]]), [1, 2, 3, 4]),
+    ?ASSERT_MATCH(lists:append([[1, 2], [a, b]]), [1, 2, a, b]),
+    ?ASSERT_MATCH(lists:append([["1", "2"], [a, b]]), ["1", "2", a, b]),
+    ?ASSERT_ERROR(lists:append(1), function_clause),
+    ?ASSERT_MATCH(lists:append("abc", "def"), "abcdef"),
+    ?ASSERT_MATCH(lists:append([1, 2], [3, 4]), [1, 2, 3, 4]),
+    ?ASSERT_ERROR(lists:append(1, 3), badarg),
+    ok.
+
 id(X) -> X.