From e32a95d9c74653c61346e83076f92bc24a648d63 Mon Sep 17 00:00:00 2001
From: Renegatto <46404781+Renegatto@users.noreply.github.com>
Date: Sat, 25 Oct 2025 02:43:44 +0300
Subject: [PATCH 1/2] Fix Semigroup.lua/concatArray misusing table.concat for
 arrays concatenation

concatArray: ([String], String, Int, Int) -> String

does not concatenate arrays, it is rather some equivalent of Array.prototype.join in JS.
---
 src/Data/Semigroup.lua | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/Data/Semigroup.lua b/src/Data/Semigroup.lua
index 22165467..6949b09a 100644
--- a/src/Data/Semigroup.lua
+++ b/src/Data/Semigroup.lua
@@ -4,7 +4,15 @@ return {
     return function(ys)
       if #xs == 0 then return ys end
       if #ys == 0 then return xs end
-      return table.concat(xs, ys)
+      local result = {}
+      for index, value in ipairs(xs) do
+        result[index] = value
+      end
+      local offset = #result
+      for index, value in ipairs(ys) do
+        result[index + offset] = value
+      end
+      return result
     end
   end)
 }

From 508b646a33f1105c5b18d46b0dedd5e9b1314ba5 Mon Sep 17 00:00:00 2001
From: Renegatto <46404781+Renegatto@users.noreply.github.com>
Date: Sat, 25 Oct 2025 02:50:03 +0300
Subject: [PATCH 2/2] Update CHANGELOG.md

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d7e5af83..27b3952a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ Breaking changes:
 New features:
 
 Bugfixes:
+- Fixed `Semigroup.append` broken for `Array` (#4 by @Renegatto)
 
 Other improvements: