Question

This is my current code:

#include <list>
#include <string>
using std::string;
using std::list;

int main()
{
    list <string> list_;
    list_.push_back("C");
    list_.push_back("a");
    list_.push_back("b");

    list_.sort();
}

Does the sort() function sort the elements according to their character codes? I want the result here to be a b C after the sorting is done.

Answer 1

The default comparator (<) using the default char_traits< char > will sort your list as C a b.

See list::sort.

In order to achieve the desired order a b C you can either:

1. compose your list of string types with custom char_traits, or

2. provide an instance of a custom string comparator to sort, e.g.

   bool istring_less(const string& lhs, const string& rhs) {
     string::const_iterator \
       lb = lhs.begin(), le = lhs.end(),
       rb = rhs.begin(), re = rhs.end();
     const char lc, rc;
     for ( ; lb != le && rb != re; ++lb, ++rb) {
       lc = tolower(*lb);
       rc = tolower(*rb);
       if (*lc < *rc) return true;
       if (*lc > *rc) return false;
     }
     // if rhs is longer than lhs then lhs<rhs
     return (rb != re);
   }
   ...
   list.sort(istring_less);