https://github.com/kpeeters/tree.hh/commit/0ee8b5a4c3a93814bbf465ffc56c296cf84f1832

From: Kasper Peeters <kasper.peeters@phi-sci.com>
Date: Fri, 17 Nov 2023 11:27:13 +0000
Subject: [PATCH] Fix const-correctness for comparison.

---
 src/tree.hh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/tree.hh b/src/tree.hh
index d460165..be45f99 100644
--- a/src/tree.hh
+++ b/src/tree.hh
@@ -505,7 +505,7 @@ class tree {
 			public:
 				compare_nodes(StrictWeakOrdering comp) : comp_(comp) {}
 				
-				bool operator()(const tree_node *a, const tree_node *b) 
+				bool operator()(const tree_node *a, const tree_node *b) const
 					{
 					return comp_(a->data, b->data);
 					}