From 7fa51328390e8c7b2d837b94171c7b39f83a2899 Mon Sep 17 00:00:00 2001
From: Sermet Pekin <sermet.pekin@gmail.com>
Date: Sun, 3 Mar 2024 10:20:37 +0300
Subject: [PATCH] minor imp

---
 src/sp_df.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/sp_df.cpp b/src/sp_df.cpp
index 634ea76..54bd6c5 100644
--- a/src/sp_df.cpp
+++ b/src/sp_df.cpp
@@ -117,7 +117,7 @@ namespace Rapi
     Rc_vec_char get_col_names(const Rc_df &dfx) { return dfx.names(); }
     Rc_vec_char get_col_names() { return df.names(); }
     //............................... col_exists
-    bool col_exists(s_string & col_name)
+    bool col_exists(const s_string & col_name)
     {
       for (const auto &x : get_col_names())
       {