From 2388be23a3ec1fe877ff8f40917c64ebfbc3b0be Mon Sep 17 00:00:00 2001
From: Rob Ward <rob@ward-software-architects.ch>
Date: Wed, 12 Jan 2022 20:05:49 +0100
Subject: [PATCH] Fix handling of UTF-8 characters in string constants

---
 exprtk.hpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/exprtk.hpp b/exprtk.hpp
index 4ce0848..69808c5 100644
--- a/exprtk.hpp
+++ b/exprtk.hpp
@@ -175,7 +175,7 @@ namespace exprtk
 
       inline bool is_valid_string_char(const char_t c)
       {
-         return std::isprint(static_cast<uchar_t>(c)) ||
+         return !std::iscntrl(static_cast<uchar_t>(c)) ||
                 is_whitespace(c);
       }