+string &append(string &str, const string &sep, const string &other)
+{
+ if(!str.empty() && !other.empty())
+ str += sep;
+ str += other;
+ return str;
+}
+
+string join(const string &str1, const string &sep, const string &str2)
+{
+ string result = str1;
+ return append(result, sep, str2);
+}
+