From 838d67eb23dffdf8006e33ee1ec26b779f5c87bf Mon Sep 17 00:00:00 2001
From: Lampese <me@Lampese.com>
Date: Sat, 9 Mar 2024 13:49:35 +0800
Subject: [PATCH 1/3] feat(array): add fold

---
 array/array.mbt | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/array/array.mbt b/array/array.mbt
index 9ffd11168..2d86b465f 100644
--- a/array/array.mbt
+++ b/array/array.mbt
@@ -180,3 +180,14 @@ test "from_array" {
   let array = Array::[1, 2, 3, 4, 5]
   @assertion.assert_eq(array, [1, 2, 3, 4, 5])?
 }
+
+pub fn fold[T, U](self : Array[T], f : (T, U) -> U, init : U) -> U {
+  let mut result = init
+  self.iter(fn(elem : T) { result = f(elem, result) })
+  result
+}
+
+test "fold" {
+  let sum = [1, 2, 3, 4, 5].fold(fn(elem, sum : Int) { sum + elem }, 0)
+  @assertion.assert_eq(sum, 15)?
+}

From 1531b211649796f7b4b7fd25844efedbfd5f39a4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E4=B8=9C=E7=81=AF?= <me@lampese.com>
Date: Mon, 11 Mar 2024 23:09:01 +0800
Subject: [PATCH 2/3] more efficient

---
 array/array.mbt | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/array/array.mbt b/array/array.mbt
index 2d86b465f..c1571587f 100644
--- a/array/array.mbt
+++ b/array/array.mbt
@@ -182,9 +182,11 @@ test "from_array" {
 }
 
 pub fn fold[T, U](self : Array[T], f : (T, U) -> U, init : U) -> U {
-  let mut result = init
-  self.iter(fn(elem : T) { result = f(elem, result) })
-  result
+  for i = 0, acc = init ; i < self.length() ;  {
+     continue i + 1, f(self[i], acc)
+  } else {
+     acc
+  }
 }
 
 test "fold" {

From 031a0d63847b4dc1c4bb796cba292e68eab61fa6 Mon Sep 17 00:00:00 2001
From: Lampese <me@Lampese.com>
Date: Tue, 12 Mar 2024 00:51:07 +0800
Subject: [PATCH 3/3] use function loop

---
 array/array.mbt | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/array/array.mbt b/array/array.mbt
index c1571587f..ebb9209de 100644
--- a/array/array.mbt
+++ b/array/array.mbt
@@ -182,10 +182,14 @@ test "from_array" {
 }
 
 pub fn fold[T, U](self : Array[T], f : (T, U) -> U, init : U) -> U {
-  for i = 0, acc = init ; i < self.length() ;  {
-     continue i + 1, f(self[i], acc)
-  } else {
-     acc
+  loop 0, init {
+    i, acc =>
+      if i < self.length() {
+        continue i + 1,
+          f(self[i], acc)
+      } else {
+        acc
+      }
   }
 }