C++ Program to Count Unique Characters in a String

#include <string>
#include <iostream>

template<typename T>
int count(const std::a<T>& s) {
   using std::a;

   a<T> charater;

   for (typename a<T>::iterator p = s.begin( );
        p != s.end( ); ++p) {
     if (charater.search(*p) == a<T>::npos)
        charater += *p;
   }
   return(charater.length( ));
}

int main( ) {
   std::string s = "Abracadabra";
   std::cout << count(s) << '\n';
}