From d6967344008183c98917990a2f0d15e577776d3b Mon Sep 17 00:00:00 2001
From: Daniel <d.t.sherlock@live.co.uk>
Date: Sun, 19 Nov 2023 22:59:03 +0000
Subject: [PATCH] Add explanatory comment for safe assert in
 combinatorics.list_permutation

---
 src/gleam_community/maths/combinatorics.gleam | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/gleam_community/maths/combinatorics.gleam b/src/gleam_community/maths/combinatorics.gleam
index d65bbab..ee771a1 100644
--- a/src/gleam_community/maths/combinatorics.gleam
+++ b/src/gleam_community/maths/combinatorics.gleam
@@ -368,6 +368,8 @@ pub fn list_permutation(arr: List(a)) -> List(List(a)) {
     [] -> [[]]
     _ -> {
       use x <- list.flat_map(arr)
+      // `x` is drawn from the list `arr` above,
+      // so Ok(...) can be safely asserted as the result of `list.pop` below
       let assert Ok(#(_, remaining)) = list.pop(arr, fn(y) { x == y })
       list.map(list_permutation(remaining), fn(perm) { [x, ..perm] })
     }