#include <string>
  iterator insert( iterator i, const char& ch );
  string& insert( size_type index, const string& str );
  string& insert( size_type index, const char* str );
  string& insert( size_type index1, const string& str, size_type index2, size_type num );
  string& insert( size_type index, const char* str, size_type num );
  string& insert( size_type index, size_type num, char ch );
  void insert( iterator i, size_type num, const char& ch );
  void insert( iterator i, iterator start, iterator end );

The very multi-purpose insert() function either:

• inserts ch before the character denoted by i,
• inserts str into the current string, at location index,
• inserts a substring of str (starting at index2 and num characters long) into the current string, at location index1,
• inserts num characters of str into the current string, at location index,
• inserts num copies of ch into the current string, at location index,
• inserts num copies of ch into the current string, before the character denoted by i,
• or inserts the characters denoted by start and end into the current string, before the character specified by i.