From f7d9e213d5c974668e855bf0fff862daef47191b Mon Sep 17 00:00:00 2001
From: Blugatroff <51498987+Blugatroff@users.noreply.github.com>
Date: Sat, 14 Jan 2023 23:49:49 +0100
Subject: [PATCH 1/3] Add length to Data.Array.ST

---
 src/Data/Array/ST.js         |  6 ++++++
 src/Data/Array/ST.purs       |  7 +++++++
 test/Test/Data/Array/ST.purs | 17 +++++++++++++++++
 3 files changed, 30 insertions(+)

diff --git a/src/Data/Array/ST.js b/src/Data/Array/ST.js
index 57709b79..24267de7 100644
--- a/src/Data/Array/ST.js
+++ b/src/Data/Array/ST.js
@@ -27,6 +27,12 @@ export const poke = function (i) {
   };
 };
 
+export const lengthImpl = function (xs) {
+  return function () {
+    return xs.length;
+  };
+};
+
 export const popImpl = function (just) {
   return function (nothing) {
     return function (xs) {
diff --git a/src/Data/Array/ST.purs b/src/Data/Array/ST.purs
index 2817bee6..9df7cebd 100644
--- a/src/Data/Array/ST.purs
+++ b/src/Data/Array/ST.purs
@@ -11,6 +11,7 @@ module Data.Array.ST
   , peek
   , poke
   , modify
+  , length
   , pop
   , push
   , pushAll
@@ -149,6 +150,12 @@ foreign import peekImpl
 -- | Change the value at the specified index in a mutable array.
 foreign import poke :: forall h a. Int -> a -> STArray h a -> ST h Boolean
 
+-- | Get the number of elements in a mutable array.
+length :: forall h a. STArray h a -> ST h Int
+length = lengthImpl
+
+foreign import lengthImpl :: forall h a. STArray h a -> ST h Int
+
 -- | Remove the last element from an array and return that element.
 pop :: forall h a. STArray h a -> ST h (Maybe a)
 pop = popImpl Just Nothing
diff --git a/test/Test/Data/Array/ST.purs b/test/Test/Data/Array/ST.purs
index 8a83cd99..6e42fc2f 100644
--- a/test/Test/Data/Array/ST.purs
+++ b/test/Test/Data/Array/ST.purs
@@ -49,6 +49,23 @@ testArrayST = do
 
   assert $ STA.run (STA.unsafeThaw [1, 2, 3]) == [1, 2, 3]
 
+  log "length should return the number of items in an STArray"
+
+  assert $ ST.run (do
+    arr <- STA.thaw nil
+    length <- STA.length arr
+    pure $ length == 0)
+
+  assert $ ST.run (do
+    arr <- STA.thaw [1]
+    length <- STA.length arr
+    pure $ length == 1)
+
+  assert $ ST.run (do
+    arr <- STA.thaw [1, 2, 3, 4, 5]
+    length <- STA.length arr
+    pure $ length == 5)
+
   log "pop should remove elements from an STArray"
 
   assert $ STA.run (do

From b518e62e1266ac06c0033be50bc50533b18babcb Mon Sep 17 00:00:00 2001
From: Blugatroff <51498987+Blugatroff@users.noreply.github.com>
Date: Sun, 15 Jan 2023 00:00:43 +0100
Subject: [PATCH 2/3] Add changelog entry

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

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 438b8d07..45640969 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ Breaking changes:
 
 New features:
 - Add `prependArray` (#224 by @JordanMartinez)
+- Add `Data.Array.ST.length` (#239 by @Blugatroff)
 
 Bugfixes:
 

From f65cbf53370c5ae564a7da7277b93d500c48d1ad Mon Sep 17 00:00:00 2001
From: Blugatroff <51498987+Blugatroff@users.noreply.github.com>
Date: Mon, 16 Jan 2023 22:56:06 +0100
Subject: [PATCH 3/3] Export foreign function directly instead of using
 `lengthImpl`.

---
 src/Data/Array/ST.js   | 2 +-
 src/Data/Array/ST.purs | 5 +----
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/src/Data/Array/ST.js b/src/Data/Array/ST.js
index 24267de7..7dfff146 100644
--- a/src/Data/Array/ST.js
+++ b/src/Data/Array/ST.js
@@ -27,7 +27,7 @@ export const poke = function (i) {
   };
 };
 
-export const lengthImpl = function (xs) {
+export const length = function (xs) {
   return function () {
     return xs.length;
   };
diff --git a/src/Data/Array/ST.purs b/src/Data/Array/ST.purs
index 9df7cebd..b4e6a87f 100644
--- a/src/Data/Array/ST.purs
+++ b/src/Data/Array/ST.purs
@@ -151,10 +151,7 @@ foreign import peekImpl
 foreign import poke :: forall h a. Int -> a -> STArray h a -> ST h Boolean
 
 -- | Get the number of elements in a mutable array.
-length :: forall h a. STArray h a -> ST h Int
-length = lengthImpl
-
-foreign import lengthImpl :: forall h a. STArray h a -> ST h Int
+foreign import length :: forall h a. STArray h a -> ST h Int
 
 -- | Remove the last element from an array and return that element.
 pop :: forall h a. STArray h a -> ST h (Maybe a)