feat: add update method

packages/incremental-merkle-tree/README.md

@@ -90,6 +90,12 @@ const tree = new IncrementalMerkleTree(poseidon, 16, BigInt(0), 2) // Binary tre
 tree.insert(BigInt(1))
 ```
 
+\# **update**(index: _number_, newLeaf: _Node_)
+
+```typescript
+tree.update(0, BigInt(2))
+```
+
 \# **delete**(index: _number_)
 
 ```typescript

packages/incremental-merkle-tree/src/incremental-merkle-tree.ts

@@ -130,6 +130,16 @@ export default class IncrementalMerkleTree {
     this._root = _update(index, this.zeroes[0], this.depth, this.arity, this._nodes, this.zeroes, this._hash)
   }
 
+  /**
+   * Deletes a leaf from the tree. It does not remove the leaf from
+   * the data structure. It set the leaf to be deleted to a zero value.
+   * @param index Index of the leaf to be deleted.
+   * @param newLeaf New leaf value.
+   */
+  public update(index: number, newLeaf: Node) {
+    this._root = _update(index, newLeaf, this.depth, this.arity, this._nodes, this.zeroes, this._hash)
+  }
+
   /**
    * Creates a proof of membership.
    * @param index Index of the proof's leaf.

packages/incremental-merkle-tree/tests/index.test.ts

@@ -89,6 +89,22 @@ describe("Incremental Merkle Tree", () => {
         }
       })
 
+      it(`Should update ${numberOfLeaves} leaves`, () => {
+        for (let i = 0; i < numberOfLeaves; i += 1) {
+          tree.insert(BigInt(1))
+          oldTree.insert(BigInt(1))
+        }
+
+        for (let i = 0; i < numberOfLeaves; i += 1) {
+          tree.update(i, BigInt(0))
+          oldTree.update(i, BigInt(0))
+
+          const { root } = oldTree.genMerklePath(0)
+
+          expect(tree.root).toEqual(root)
+        }
+      })
+
       it("Should return the index of a leaf", () => {
         tree.insert(BigInt(1))
         tree.insert(BigInt(2))