From 4d2262600ee6da2d108e553d4fb06df1c6aa7857 Mon Sep 17 00:00:00 2001
From: Alexandre Duret-Lutz <adl@lrde.epita.fr>
Date: Thu, 2 Dec 2021 17:31:47 +0100
Subject: [PATCH] formula: is_literal should be const

Reported by Ayrat Khalimov.

* spot/tl/formula.hh (is_literal): Mark as const.
---
 spot/tl/formula.hh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/spot/tl/formula.hh b/spot/tl/formula.hh
index a323dcdaf..c52ed3e39 100644
--- a/spot/tl/formula.hh
+++ b/spot/tl/formula.hh
@@ -1557,7 +1557,7 @@ namespace spot
 
     /// \brief Whether the formula is an atomic proposition or its
     /// negation.
-    bool is_literal()
+    bool is_literal() const
     {
       return (is(op::ap) ||
           // If f is in nenoform, Not can only occur in front of