From 109d41142f8dc89d692571d5fd1bf20e236b89ee Mon Sep 17 00:00:00 2001
From: Tianpu Zhao <pacosynthesis@gmail.com>
Date: Thu, 23 Jun 2022 13:27:24 -0700
Subject: [PATCH] Fixed the Issue #139 on identifying loops in circuits with
 more than 1 capacitor islands

---
 scqubits/core/circuit.py          |  4 ++--
 scqubits/core/symbolic_circuit.py | 12 ++++++------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/scqubits/core/circuit.py b/scqubits/core/circuit.py
index 44f7364d..7a505eb9 100644
--- a/scqubits/core/circuit.py
+++ b/scqubits/core/circuit.py
@@ -1805,14 +1805,14 @@ def sym_hamiltonian(
             )
         else:
             sym_hamiltonian = sm.Add(
-                sm.UnevaluatedExpr(
+                (
                     self._make_expr_human_readable(
                         self.hamiltonian_symbolic.expand()
                         - self.potential_symbolic.expand(),
                         float_round=float_round,
                     )
                 ),
-                sm.UnevaluatedExpr(
+                (
                     self._make_expr_human_readable(
                         self.potential_symbolic.expand(), float_round=float_round
                     )
diff --git a/scqubits/core/symbolic_circuit.py b/scqubits/core/symbolic_circuit.py
index 4fcd4c08..888cee83 100644
--- a/scqubits/core/symbolic_circuit.py
+++ b/scqubits/core/symbolic_circuit.py
@@ -1463,19 +1463,19 @@ def _find_loop(self, closure_branch: Branch) -> List["Branch"]:
         gen_1, ancestors_1, path_1 = self._find_path_to_root(closure_branch.nodes[0])
         gen_2, ancestors_2, path_2 = self._find_path_to_root(closure_branch.nodes[1])
         # find the first common ancestor of these two nodes
-        # start from the root node, find out the last generation where two nodes have the
+        # start from the root node, find out the last sub-generation where two nodes have the
         # same ancestor
-        gen_last_same_ancestor = 0
-        for igen in range(min(gen_1, gen_2)):
+        sub_gen_last_same_ancestor = -1
+        for igen in range(min(len(ancestors_1), len(ancestors_2))):
             if ancestors_1[igen].id == ancestors_2[igen].id:
-                gen_last_same_ancestor = igen
+                sub_gen_last_same_ancestor = igen
             elif ancestors_1[igen].id != ancestors_2[igen].id:
                 break
         # get all the branches of the paths from the two nodes to the root, after the last
         # shared ancestor, and the closure branch itself
         loop = (
-            path_1[gen_last_same_ancestor:]
-            + path_2[gen_last_same_ancestor:]
+            path_1[sub_gen_last_same_ancestor+1:]
+            + path_2[sub_gen_last_same_ancestor+1:]
             + [closure_branch]
         )
         return loop