rename `list.flatten` to `list.concat` (#477)

5 files changed, 30 insertions, 29 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0b2e66b..18f9c04 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## Unreleased
 
 - The `list` module gains the `list.map2` function.
+- `flatten` has been renamed to `concat` in the `list` module.
 
 ## v0.29.2 - 2023-06-21
 
diff --git a/src/gleam/dynamic.gleam b/src/gleam/dynamic.gleam
index 86055a0..f6b1717 100644
--- a/src/gleam/dynamic.gleam
+++ b/src/gleam/dynamic.gleam
@@ -1190,7 +1190,7 @@ pub fn decode2(
   fn(value) {
     case t1(value), t2(value) {
       Ok(a), Ok(b) -> Ok(constructor(a, b))
-      a, b -> Error(list.flatten([all_errors(a), all_errors(b)]))
+      a, b -> Error(list.concat([all_errors(a), all_errors(b)]))
     }
   }
 }
@@ -1224,7 +1224,7 @@ pub fn decode3(
     case t1(value), t2(value), t3(value) {
       Ok(a), Ok(b), Ok(c) -> Ok(constructor(a, b, c))
       a, b, c ->
-        Error(list.flatten([all_errors(a), all_errors(b), all_errors(c)]))
+        Error(list.concat([all_errors(a), all_errors(b), all_errors(c)]))
     }
   }
 }
@@ -1271,7 +1271,7 @@ pub fn decode4(
     case t1(x), t2(x), t3(x), t4(x) {
       Ok(a), Ok(b), Ok(c), Ok(d) -> Ok(constructor(a, b, c, d))
       a, b, c, d ->
-        Error(list.flatten([
+        Error(list.concat([
           all_errors(a),
           all_errors(b),
           all_errors(c),
@@ -1326,7 +1326,7 @@ pub fn decode5(
     case t1(x), t2(x), t3(x), t4(x), t5(x) {
       Ok(a), Ok(b), Ok(c), Ok(d), Ok(e) -> Ok(constructor(a, b, c, d, e))
       a, b, c, d, e ->
-        Error(list.flatten([
+        Error(list.concat([
           all_errors(a),
           all_errors(b),
           all_errors(c),
@@ -1386,7 +1386,7 @@ pub fn decode6(
       Ok(a), Ok(b), Ok(c), Ok(d), Ok(e), Ok(f) ->
         Ok(constructor(a, b, c, d, e, f))
       a, b, c, d, e, f ->
-        Error(list.flatten([
+        Error(list.concat([
           all_errors(a),
           all_errors(b),
           all_errors(c),
@@ -1450,7 +1450,7 @@ pub fn decode7(
       Ok(a), Ok(b), Ok(c), Ok(d), Ok(e), Ok(f), Ok(g) ->
         Ok(constructor(a, b, c, d, e, f, g))
       a, b, c, d, e, f, g ->
-        Error(list.flatten([
+        Error(list.concat([
           all_errors(a),
           all_errors(b),
           all_errors(c),
@@ -1518,7 +1518,7 @@ pub fn decode8(
       Ok(a), Ok(b), Ok(c), Ok(d), Ok(e), Ok(f), Ok(g), Ok(h) ->
         Ok(constructor(a, b, c, d, e, f, g, h))
       a, b, c, d, e, f, g, h ->
-        Error(list.flatten([
+        Error(list.concat([
           all_errors(a),
           all_errors(b),
           all_errors(c),
@@ -1590,7 +1590,7 @@ pub fn decode9(
       Ok(a), Ok(b), Ok(c), Ok(d), Ok(e), Ok(f), Ok(g), Ok(h), Ok(i) ->
         Ok(constructor(a, b, c, d, e, f, g, h, i))
       a, b, c, d, e, f, g, h, i ->
-        Error(list.flatten([
+        Error(list.concat([
           all_errors(a),
           all_errors(b),
           all_errors(c),
diff --git a/src/gleam/list.gleam b/src/gleam/list.gleam
index b1acb74..ed1d718 100644
--- a/src/gleam/list.gleam
+++ b/src/gleam/list.gleam
@@ -660,30 +660,30 @@ fn reverse_and_prepend(list prefix: List(a), to suffix: List(a)) -> List(a) {
   }
 }
 
-fn do_flatten(lists: List(List(a)), acc: List(a)) -> List(a) {
+fn do_concat(lists: List(List(a)), acc: List(a)) -> List(a) {
   case lists {
     [] -> reverse(acc)
     [list, ..further_lists] ->
-      do_flatten(further_lists, reverse_and_prepend(list: list, to: acc))
+      do_concat(further_lists, reverse_and_prepend(list: list, to: acc))
   }
 }
 
-/// Flattens a list of lists into a single list.
+/// Joins a list of lists into a single list.
 ///
 /// This function traverses all elements twice.
 ///
 /// ## Examples
 ///
 /// ```gleam
-/// > flatten([[1], [2, 3], []])
+/// > concat([[1], [2, 3], []])
 /// [1, 2, 3]
 /// ```
 ///
-pub fn flatten(lists: List(List(a))) -> List(a) {
-  do_flatten(lists, [])
+pub fn concat(lists: List(List(a))) -> List(a) {
+  do_concat(lists, [])
 }
 
-/// Maps the list with the given function and then flattens it.
+/// Maps the list with the given function into a list of lists, and then flattens it.
 ///
 /// ## Examples
 ///
@@ -694,7 +694,7 @@ pub fn flatten(lists: List(List(a))) -> List(a) {
 ///
 pub fn flat_map(over list: List(a), with fun: fn(a) -> List(b)) -> List(b) {
   map(list, fun)
-  |> flatten
+  |> concat
 }
 
 /// Reduces a list of elements into a single value by calling a given function
@@ -1684,7 +1684,7 @@ pub fn permutations(l: List(a)) -> List(List(a)) {
         |> permutations
         |> map(fn(permutation) { [i, ..permutation] })
       })
-      |> flatten
+      |> concat
   }
 }
 
@@ -2012,7 +2012,7 @@ fn do_combination_pairs(items: List(a)) -> List(List(#(a, a))) {
 ///
 pub fn combination_pairs(items: List(a)) -> List(#(a, a)) {
   do_combination_pairs(items)
-  |> flatten
+  |> concat
 }
 
 /// Make a list alternating the elements from the given lists
@@ -2026,7 +2026,7 @@ pub fn combination_pairs(items: List(a)) -> List(#(a, a)) {
 ///
 pub fn interleave(list: List(List(a))) -> List(a) {
   transpose(list)
-  |> flatten
+  |> concat
 }
 
 /// Transpose rows and columns of the list of lists.
@@ -2058,7 +2058,7 @@ pub fn transpose(list_of_list: List(List(a))) -> List(List(a)) {
       let firsts =
         rows
         |> map(take_first)
-        |> flatten
+        |> concat
       let rest = transpose(map(rows, drop(_, 1)))
       [firsts, ..rest]
     }
diff --git a/test/gleam/iterator_test.gleam b/test/gleam/iterator_test.gleam
index 5348183..bb9a825 100644
--- a/test/gleam/iterator_test.gleam
+++ b/test/gleam/iterator_test.gleam
@@ -167,7 +167,7 @@ pub fn flat_map_test() {
       subject
       |> list.map(f)
       |> list.map(iterator.to_list)
-      |> list.flatten,
+      |> list.concat,
     )
   }
 
@@ -185,7 +185,7 @@ pub fn append_test() {
     |> iterator.from_list
     |> iterator.append(iterator.from_list(right))
     |> iterator.to_list
-    |> should.equal(list.flatten([left, right]))
+    |> should.equal(list.concat([left, right]))
   }
 
   test([], [])
@@ -201,7 +201,7 @@ pub fn flatten_test() {
     |> iterator.from_list
     |> iterator.flatten
     |> iterator.to_list
-    |> should.equal(list.flatten(lists))
+    |> should.equal(list.concat(lists))
   }
 
   test([[], []])
diff --git a/test/gleam/list_test.gleam b/test/gleam/list_test.gleam
index bf8bb2a..2883535 100644
--- a/test/gleam/list_test.gleam
+++ b/test/gleam/list_test.gleam
@@ -287,23 +287,23 @@ pub fn append_test() {
   |> list.append([1])
 }
 
-pub fn flatten_test() {
-  list.flatten([])
+pub fn concat_test() {
+  list.concat([])
   |> should.equal([])
 
-  list.flatten([[]])
+  list.concat([[]])
   |> should.equal([])
 
-  list.flatten([[], [], []])
+  list.concat([[], [], []])
   |> should.equal([])
 
-  list.flatten([[1, 2], [], [3, 4]])
+  list.concat([[1, 2], [], [3, 4]])
   |> should.equal([1, 2, 3, 4])
   // // TCO test
   // case recursion_test_cycles > 2 {
   //   True ->
   //     list.repeat([[1]], recursion_test_cycles / 50)
-  //     |> list.flatten()
+  //     |> list.concat()
   //   False -> []
   // }
 }