diff options
| -rw-r--r-- | src/gleam/list.gleam | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/src/gleam/list.gleam b/src/gleam/list.gleam index b4c24c3..ddb062a 100644 --- a/src/gleam/list.gleam +++ b/src/gleam/list.gleam @@ -530,17 +530,24 @@ pub fn prepend(to list: List(a), item: a) -> List(a) { [item, ..list] } +fn prepend_list_reverse(list prefix: List(a), to suffix: List(a)) -> List(a) { + case prefix { + [] -> suffix + [head, ..tail] -> prepend_list_reverse(tail, [head, ..suffix]) + } +} + fn do_flatten(lists: List(List(a)), acc: List(a)) -> List(a) { case lists { - [] -> acc - [l, ..rest] -> do_flatten(rest, append(acc, l)) + [] -> reverse(acc) + [a_list, ..rest_lists] -> + do_flatten(rest_lists, prepend_list_reverse(a_list, acc)) } } /// Flattens a list of lists into a single list. /// -/// This function runs in linear time, and it traverses and copies all the -/// inner lists. +/// This function traverses all elements twice. /// /// ## Examples /// |