add string replace function

include/toolkit.h

@@ -2,10 +2,11 @@
 #define TOOLKIT_H
 
 #include <charconv>
+#include <cstring>
 #include <expected>
 #include <type_traits>
-#include <string_view>
 #include <string>
+#include <cstdlib>
 #include <ios>
 
 //use for to_chars
@@ -44,6 +45,28 @@ namespace toolkit{
         }
         return value;
     }
+
+    template <typename T>
+    requires std::is_same_v<std::string, T> || std::is_same_v<const char*, T>
+    std::string replace_string(const std::string& str, T d, T e){
+        std::string result = str;
+        if(d == e){
+            return result;
+        }
+        size_t len = 0;
+        while(true){
+            auto pos = result.find_first_of(d);
+            if(pos == std::string::npos){
+                return result;
+            }
+            if constexpr(std::is_same_v<T, const char*>){
+                len = std::strlen(d);
+            }else{
+                len = d.length();
+            }
+            result = result.replace(pos, len ,e);
+        }
+    }
 }
 
 #endif