From 667c57a8354c5e6f3d6f7340e512fb29f8be9613 Mon Sep 17 00:00:00 2001
From: Kris Nuttycombe <kris@nutty.land>
Date: Thu, 4 May 2023 12:49:16 -0600
Subject: [PATCH] Avoid a few usize-u8 comparisons.

---
 incrementalmerkletree/src/frontier.rs | 6 +++---
 incrementalmerkletree/src/lib.rs      | 9 ++++-----
 incrementalmerkletree/src/witness.rs  | 6 +++---
 3 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/incrementalmerkletree/src/frontier.rs b/incrementalmerkletree/src/frontier.rs
index 5cb8c1f..d19e433 100644
--- a/incrementalmerkletree/src/frontier.rs
+++ b/incrementalmerkletree/src/frontier.rs
@@ -477,9 +477,9 @@ impl<H: Hashable + Clone, const DEPTH: u8> CommitmentTree<H, DEPTH> {
             .iter()
             .chain(repeat(&None))
             .take((depth - 1).into())
-            .enumerate()
-            .fold(leaf_root, |root, (i, p)| {
-                let level = Level::from(i as u8 + 1);
+            .zip(0u8..)
+            .fold(leaf_root, |root, (p, i)| {
+                let level = Level::from(i + 1);
                 match p {
                     Some(node) => H::combine(level, node, &root),
                     None => H::combine(level, &root, &filler.next(level)),
diff --git a/incrementalmerkletree/src/lib.rs b/incrementalmerkletree/src/lib.rs
index 42d53de..2732368 100644
--- a/incrementalmerkletree/src/lib.rs
+++ b/incrementalmerkletree/src/lib.rs
@@ -499,13 +499,12 @@ impl<H: Hashable, const DEPTH: u8> MerklePath<H, DEPTH> {
     pub fn root(&self, leaf: H) -> H {
         self.path_elems
             .iter()
-            .enumerate()
-            .fold(leaf, |root, (i, h)| {
-                let level = Level(i as u8);
+            .zip(0u8..)
+            .fold(leaf, |root, (h, i)| {
                 if (self.position.0 >> i) & 0x1 == 0 {
-                    H::combine(level, &root, h)
+                    H::combine(i.into(), &root, h)
                 } else {
-                    H::combine(level, h, &root)
+                    H::combine(i.into(), h, &root)
                 }
             })
     }
diff --git a/incrementalmerkletree/src/witness.rs b/incrementalmerkletree/src/witness.rs
index 5bbe20d..41d9c38 100644
--- a/incrementalmerkletree/src/witness.rs
+++ b/incrementalmerkletree/src/witness.rs
@@ -195,17 +195,17 @@ impl<H: Hashable + Clone, const DEPTH: u8> IncrementalWitness<H, DEPTH> {
             return None;
         }
 
-        for (i, p) in self
+        for (p, i) in self
             .tree
             .parents
             .iter()
             .chain(repeat(&None))
             .take((depth - 1).into())
-            .enumerate()
+            .zip(0u8..)
         {
             auth_path.push(match p {
                 Some(node) => node.clone(),
-                None => filler.next(Level::from((i + 1) as u8)),
+                None => filler.next(Level::from(i + 1)),
             });
         }