From 03647457d9390ff7fdb6f939d32ece3676ca4303 Mon Sep 17 00:00:00 2001
From: Serge Radinovich <47865535+sergerad@users.noreply.github.com>
Date: Mon, 5 May 2025 13:46:54 +1200
Subject: [PATCH] Add default constructors to MmrPeaks and PartialMmr (#409)

---
 CHANGELOG.md                           |  1 +
 miden-crypto/src/merkle/mmr/partial.rs | 12 ++++++++++++
 miden-crypto/src/merkle/mmr/peaks.rs   |  7 +++++++
 miden-crypto/src/merkle/mmr/tests.rs   | 17 +++++++++++++++++
 4 files changed, 37 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 48247a6..4a7928b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 ## 0.15.0 (TBD)
 
+- Added default constructors to `MmrPeaks` and `PartialMmr` (#409).
 
 ## 0.14.0 (2025-03-15)
 
diff --git a/miden-crypto/src/merkle/mmr/partial.rs b/miden-crypto/src/merkle/mmr/partial.rs
index 1cf2fd2..310f55e 100644
--- a/miden-crypto/src/merkle/mmr/partial.rs
+++ b/miden-crypto/src/merkle/mmr/partial.rs
@@ -70,6 +70,18 @@ pub struct PartialMmr {
     pub(crate) track_latest: bool,
 }
 
+impl Default for PartialMmr {
+    /// Creates a new [PartialMmr] with default values.
+    fn default() -> Self {
+        let forest = 0;
+        let peaks = Vec::new();
+        let nodes = BTreeMap::new();
+        let track_latest = false;
+
+        Self { forest, peaks, nodes, track_latest }
+    }
+}
+
 impl PartialMmr {
     // CONSTRUCTORS
     // --------------------------------------------------------------------------------------------
diff --git a/miden-crypto/src/merkle/mmr/peaks.rs b/miden-crypto/src/merkle/mmr/peaks.rs
index a640afd..2873e44 100644
--- a/miden-crypto/src/merkle/mmr/peaks.rs
+++ b/miden-crypto/src/merkle/mmr/peaks.rs
@@ -34,6 +34,13 @@ pub struct MmrPeaks {
     peaks: Vec<RpoDigest>,
 }
 
+impl Default for MmrPeaks {
+    /// Returns new [`MmrPeaks`] instantiated from an empty vector of peaks and 0 leaves.
+    fn default() -> Self {
+        Self { num_leaves: 0, peaks: Vec::new() }
+    }
+}
+
 impl MmrPeaks {
     // CONSTRUCTOR
     // --------------------------------------------------------------------------------------------
diff --git a/miden-crypto/src/merkle/mmr/tests.rs b/miden-crypto/src/merkle/mmr/tests.rs
index e47a7c3..ba2ef7a 100644
--- a/miden-crypto/src/merkle/mmr/tests.rs
+++ b/miden-crypto/src/merkle/mmr/tests.rs
@@ -12,6 +12,23 @@ use crate::{
     merkle::{InOrderIndex, MerklePath, MerkleTree, MmrProof, NodeIndex, int_to_node},
 };
 
+#[test]
+fn tests_empty_mmr_peaks() {
+    let peaks = MmrPeaks::default();
+    assert_eq!(peaks.num_peaks(), 0);
+    assert_eq!(peaks.num_leaves(), 0);
+}
+
+#[test]
+fn test_empty_partial_mmr() {
+    let mmr = PartialMmr::default();
+    assert_eq!(mmr.num_leaves(), 0);
+    assert_eq!(mmr.forest(), 0);
+    assert_eq!(mmr.peaks(), MmrPeaks::default());
+    assert!(mmr.nodes.is_empty());
+    assert!(!mmr.track_latest);
+}
+
 #[test]
 fn test_position_equal_or_higher_than_leafs_is_never_contained() {
     let empty_forest = 0;