list:repeat

5 files changed, 47 insertions, 3 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 91d8232..02cb49d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,7 +5,7 @@
 - The `map_dict` module gains `update`, `merge` and `delete` functions.
 - The `bool` module gains a `compare` function.
 - The `int` module gains a `compare` function.
-- The `list` module gains `range`, and `strict_zip` functions.
+- The `list` module gains `range`, `repeat`, and `strict_zip` functions.
 
 ## v0.1.2 - 2019-04-25
 
diff --git a/gen/src/list.erl b/gen/src/list.erl
index 3170ec2..96dd7d2 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, index_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, strict_zip/2, intersperse/2, at/2, unique/1, sort/1, range/2]).
+-export([length/1, reverse/1, is_empty/1, contains/2, head/1, tail/1, filter/2, map/2, index_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, strict_zip/2, intersperse/2, at/2, unique/1, sort/1, range/2, repeat/2]).
 
 length(A) ->
     erlang:length(A).
@@ -319,3 +319,15 @@ range(Start, Stop) ->
         lt ->
             [Start | range(Start + 1, Stop)]
     end.
+
+do_repeat(A, Times, Acc) ->
+    case Times =< 0 of
+        true ->
+            Acc;
+
+        false ->
+            do_repeat(A, Times - 1, [A | Acc])
+    end.
+
+repeat(A, Times) ->
+    do_repeat(A, Times, []).
diff --git a/gen/test/list_test.erl b/gen/test/list_test.erl
index 14e204b..b00d507 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, strict_zip_test/0, intersperse_test/0, at_test/0, unique_test/0, sort_test/0, index_map_test/0, range_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, strict_zip_test/0, intersperse_test/0, at_test/0, unique_test/0, sort_test/0, index_map_test/0, range_test/0, repeat_test/0]).
 
 length_test() ->
     expect:equal(list:length([]), 0),
@@ -155,3 +155,10 @@ range_test() ->
     expect:equal(list:range(0, 1), [0]),
     expect:equal(list:range(0, 5), [0, 1, 2, 3, 4]),
     expect:equal(list:range(1, -5), [1, 0, -1, -2, -3, -4]).
+
+repeat_test() ->
+    expect:equal(list:repeat(1, -10), []),
+    expect:equal(list:repeat(1, 0), []),
+    expect:equal(list:repeat(2, 3), [2, 2, 2]),
+    expect:equal(list:repeat(<<"x">>, 5),
+                 [<<"x">>, <<"x">>, <<"x">>, <<"x">>, <<"x">>]).
diff --git a/src/list.gleam b/src/list.gleam
index 288d971..352fc77 100644
--- a/src/list.gleam
+++ b/src/list.gleam
@@ -263,3 +263,14 @@ pub fn range(start, stop) {
   | order:Lt -> [start | range(start + 1, stop)]
   }
 }
+
+fn do_repeat(a, times, acc) {
+  case times <= 0 {
+    | True -> acc
+    | False -> do_repeat(a, times - 1, [a | acc])
+  }
+}
+
+pub fn repeat(a, times) {
+  do_repeat(a, times, [])
+}
diff --git a/test/list_test.gleam b/test/list_test.gleam
index ef80223..fb32387 100644
--- a/test/list_test.gleam
+++ b/test/list_test.gleam
@@ -298,3 +298,17 @@ pub fn range_test() {
   list:range(1, -5)
   |> expect:equal(_, [1, 0, -1, -2, -3, -4])
 }
+
+pub fn repeat_test() {
+  list:repeat(1, -10)
+  |> expect:equal(_, [])
+
+  list:repeat(1, 0)
+  |> expect:equal(_, [])
+
+  list:repeat(2, 3)
+  |> expect:equal(_, [2, 2, 2])
+
+  list:repeat("x", 5)
+  |> expect:equal(_, ["x", "x", "x", "x", "x"])
+}