list:range

5 files changed, 54 insertions, 3 deletions

diff --git a/gen/src/list.erl b/gen/src/list.erl
index 36fb42d..85df70e 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, intersperse/2, at/2, unique/1, sort/1]).
+-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, intersperse/2, at/2, unique/1, sort/1, range/2]).
 
 length(A) ->
     erlang:length(A).
@@ -298,3 +298,15 @@ sort(List) ->
             BList = drop(List, SplitLength),
             merge_sort(sort(AList), sort(BList))
     end.
+
+range(Start, Stop) ->
+    case int:compare(Start, Stop) of
+        eq ->
+            [];
+
+        gt ->
+            [Start | range(Start - 1, Stop)];
+
+        lt ->
+            [Start | range(Start + 1, Stop)]
+    end.
diff --git a/gen/test/list_test.erl b/gen/test/list_test.erl
index 3011c7e..ca76423 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, intersperse_test/0, at_test/0, unique_test/0, sort_test/0, index_map_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, index_map_test/0, range_test/0]).
 
 length_test() ->
     expect:equal(list:length([]), 0),
@@ -139,3 +139,11 @@ index_map_test() ->
     F = fun(I, X) -> str:append(X, int:to_string(I)) end,
     expect:equal(list:index_map([<<"a">>, <<"b">>, <<"c">>], F),
                  [<<"a0">>, <<"b1">>, <<"c2">>]).
+
+range_test() ->
+    expect:equal(list:range(0, 0), []),
+    expect:equal(list:range(1, 1), []),
+    expect:equal(list:range(-1, -1), []),
+    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]).
diff --git a/src/bool.gleam b/src/bool.gleam
index d1d9ac4..46cca60 100644
--- a/src/bool.gleam
+++ b/src/bool.gleam
@@ -12,7 +12,7 @@ pub fn negate(bool) {
 //   | {True, True} -> order:Eq
 //   | {True, False} -> order:Gt
 //   | {False, False} -> order:Eq
-//   | {False, True} -> order:Gt
+//   | {False, True} -> order:Lt
 //   }
 // }
 
diff --git a/src/list.gleam b/src/list.gleam
index 6bcebb2..dd8fb8a 100644
--- a/src/list.gleam
+++ b/src/list.gleam
@@ -1,3 +1,6 @@
+import int
+import order
+
 pub enum Empty =
   | Empty
 
@@ -242,3 +245,11 @@ pub fn sort(list) {
     merge_sort(sort(a_list), sort(b_list))
   }
 }
+
+pub fn range(start, stop) {
+  case int:compare(start, stop) {
+  | order:Eq -> []
+  | order:Gt -> [start | range(start - 1, stop)]
+  | order:Lt -> [start | range(start + 1, stop)]
+  }
+}
diff --git a/test/list_test.gleam b/test/list_test.gleam
index ba5c4c5..81f2427 100644
--- a/test/list_test.gleam
+++ b/test/list_test.gleam
@@ -261,3 +261,23 @@ pub fn index_map_test() {
   list:index_map(["a", "b", "c"], f)
   |> expect:equal(_, ["a0", "b1", "c2"])
 }
+
+pub fn range_test() {
+  list:range(0, 0)
+  |> expect:equal(_, [])
+
+  list:range(1, 1)
+  |> expect:equal(_, [])
+
+  list:range(-1, -1)
+  |> expect:equal(_, [])
+
+  list:range(0, 1)
+  |> expect:equal(_, [0])
+
+  list:range(0, 5)
+  |> expect:equal(_, [0, 1, 2, 3, 4])
+
+  list:range(1, -5)
+  |> expect:equal(_, [1, 0, -1, -2, -3, -4])
+}