C++ Mathematical Expression Library (ExprTk)  http://www.partow.net/programming/exprtk/index.html

exprtk.hpp

diff --git a/exprtk.hpp b/exprtk.hpp
index 42d5a7d..3f49ae5 100644
--- a/exprtk.hpp
+++ b/exprtk.hpp
@@ -19309,7 +19309,12 @@
                   return error_node();
                }
 
-               expression_node_ptr default_statement = parse_multi_sequence("switch-default");
+               expression_node_ptr default_statement = error_node();
+
+               if (token_is(token_t::e_lcrlbracket,false))
+                  default_statement = parse_multi_sequence("switch-default");
+               else
+                  default_statement = parse_expression();
 
                if (0 == default_statement)
                   return error_node();