From cf8e4f7003715e7472e02a6d254592af26a0a2e8 Mon Sep 17 00:00:00 2001
From: Ronno Das <ronnodas@gmail.com>
Date: Sat, 8 Aug 2026 04:52:42 +0530
Subject: [PATCH 1/3] Add `size_hint()` for `ArrayWindows`

---
 src/array_impl.rs | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/array_impl.rs b/src/array_impl.rs
index f22739213..78d9dafd6 100644
--- a/src/array_impl.rs
+++ b/src/array_impl.rs
@@ -76,6 +76,19 @@ where
             },
         }
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let inner_sh = self.iter.size_hint();
+        if self.inner.is_none() {
+            if N == 0 {
+                size_hint::add_scalar(inner_sh, 1)
+            } else {
+                size_hint::sub_scalar(inner_sh, N - 1)
+            }
+        } else {
+            inner_sh
+        }
+    }
 }
 
 pub fn array_windows<I, const N: usize>(iter: I) -> ArrayWindows<I, N>

From 2bce804cfe03d49a3fa469ab212a1d985cb4c6e2 Mon Sep 17 00:00:00 2001
From: Ronno Das <ronnodas@gmail.com>
Date: Sat, 8 Aug 2026 04:53:57 +0530
Subject: [PATCH 2/3] Implement `ExactSizeIterator` for `ArrayWindows<I, N>`
 for small positive `N`

---
 src/array_impl.rs | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/array_impl.rs b/src/array_impl.rs
index 78d9dafd6..c2e93e755 100644
--- a/src/array_impl.rs
+++ b/src/array_impl.rs
@@ -1,4 +1,4 @@
-use crate::Itertools;
+use crate::{size_hint, Itertools};
 use std::iter::Fuse;
 
 /// An iterator over all contiguous windows of the input iterator,
@@ -102,6 +102,17 @@ where
     }
 }
 
+macro_rules! array_windows_exact_size {
+    ($($n: literal),*) => {
+        $(
+            impl<I: ExactSizeIterator<Item: Clone>> ExactSizeIterator for ArrayWindows<I, $n> {}
+        )*
+    };
+}
+
+// cannot be implemented for `N == 0` since it increases the length
+array_windows_exact_size!(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12);
+
 /// An iterator over all windows, wrapping back to the first elements when the
 /// window would otherwise exceed the length of the iterator, producing arrays
 /// of a specific size.

From 8fa10a3eebba66cbf54ce7fca5eb80690870eb3f Mon Sep 17 00:00:00 2001
From: Ronno Das <ronnodas@gmail.com>
Date: Sat, 8 Aug 2026 04:58:31 +0530
Subject: [PATCH 3/3] add tests

---
 tests/quick.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tests/quick.rs b/tests/quick.rs
index b4129a305..f5978606a 100644
--- a/tests/quick.rs
+++ b/tests/quick.rs
@@ -1337,6 +1337,15 @@ quickcheck! {
         true
     }
 
+    fn array_windows_exact_size_1(a: Vec<u8>) -> bool {
+        exact_size(a.iter().array_windows::<1>())
+    }
+
+    fn array_windows_exact_size_4(a: Vec<u8>) -> bool {
+        exact_size(a.iter().array_windows::<4>())
+    }
+
+
     fn equal_circular_array_windows_0(a: Vec<u8>) -> bool {
         let x = a.iter().map(|_| [&0u8; 0] );
         let y = a.iter().circular_array_windows::<0>();