lists_SUITE: Extend flatten/1 test to also test flatlength/1

1 files changed, 17 insertions, 11 deletions

diff --git a/lib/stdlib/test/lists_SUITE.erl b/lib/stdlib/test/lists_SUITE.erl
index 4a15bb9b81..e0dd34e82d 100644
--- a/lib/stdlib/test/lists_SUITE.erl
+++ b/lib/stdlib/test/lists_SUITE.erl
@@ -2326,18 +2326,24 @@ sublist_3_e(Config) when is_list(Config) ->
 -define(flatten_error1(X), ?line {'EXIT', _} = (catch lists:flatten(X))).
 -define(flatten_error2(X,Y), ?line {'EXIT', _} = (catch lists:flatten(X,Y))).
 
-flatten_1(doc) ->   ["flatten/1"];
-flatten_1(suite) -> [];
+%% Test lists:flatten/1,2 and lists:flatlength/1.
 flatten_1(Config) when is_list(Config) ->
-    ?line [] = lists:flatten([]),
-    ?line [1,2] = lists:flatten([1,2]),
-    ?line [1,2] = lists:flatten([1,[2]]),
-    ?line [1,2] = lists:flatten([[1],2]),
-    ?line [1,2] = lists:flatten([[1],[2]]),
-    ?line [1,2] = lists:flatten([[1,2]]),
-    ?line [a,b,c,d] = lists:flatten([[a],[b,c,[d]]]),
-
-    ok.
+    [] = lists_flatten([]),
+    [1,2] = lists_flatten([1,2]),
+    [1,2] = lists_flatten([1,[2]]),
+    [1,2] = lists_flatten([[1],2]),
+    [1,2] = lists_flatten([[1],[2]]),
+    [1,2] = lists_flatten([[1,2]]),
+    [a,b,c,d] = lists_flatten([[a],[b,c,[d]]]),
+
+    ok.
+
+lists_flatten(List) ->
+    Flat = lists:flatten(List),
+    Flat = lists:flatten(List, []),
+    Len = lists:flatlength(List),
+    Len = length(Flat),
+    Flat.
 
 flatten_1_e(doc) ->   ["flatten/1 error cases"];
 flatten_1_e(suite) -> [];