Шаблонная функция для поиска в stl-контейнерах

#include <iostream>
#include <iterator>
#include <vector>
#include <string>
using namespace std;
namespace my_sweet_dreams
{
template<typename Fwd_it>
Fwd_it
find(Fwd_it left, Fwd_it right,
     const typename iterator_traits<Fwd_it>::value_type& val)
    { 
        while(left!=right)
        {
            if(*left==val) break;
            ++left;
        }
        return left;
    }
}
 
 
int main()
{
    string mama="mama";
    auto find_a= my_sweet_dreams::find(mama.begin(), mama.end(), 'a');
    cout<<*find_a<<" has found at "<<(find_a-mama.begin())<<endl;
    string papa="papa", me="me";
    vector<string>vs{mama, me, papa};
    auto find_me= my_sweet_dreams::find(vs.begin(), vs.end(), "me");
    cout<<*find_me<<" has found at "<<(find_me-vs.begin())<<endl;
    return 0;
}

class String
{
private:
char* str;
public:
String();
 
vector <char> :: iterator <begin()>;
vector <char> :: iterator <end()>;
 
String operator==(String &obj2){
if( strcmp(str,obj2.str)){
cout<<"Не равны!"<<endl;
cout<<str;
cout<<obj2.str;
}
else
cout<<"Равны!"<<endl;
}
 
String operator!=(String &obj2){
strcmp(str,obj2.str);
if( !strcmp(str,obj2.str)){
cout<<"Равны!"<<endl;
}
else
cout<<"Не равны!"<<endl;
}
};

#include <iostream>
#include <iterator>
#include <vector>
#include <string>
#include <algorithm>
using namespace std;
namespace my_sweet_dreams
{
template<typename Fwd_it>
Fwd_it
find(Fwd_it left, Fwd_it right,
     const typename iterator_traits<Fwd_it>::value_type& val)
    {
        Fwd_it start=left;
 
        while(start!=right)
        {
            if(*start==val) break;
            ++start;
        }
        return start;
    }
}
 
class Stringer
{
  public:
   operator==(const Stringer &other)
   {
       return data == other.data;
   }
   using iterator = vector<char>::iterator;
   using const_iterator = vector<char>::const_iterator;
 
   iterator begin(){return data.begin();}
   iterator end(){return data.end()-1;}
 
   const_iterator cbegin()const{return data.cbegin();}
   const_iterator cend()const{return data.cend()-1;}
 
   Stringer(const string &str=string{})
   {
     copy(str.begin(), str.end(), back_inserter(data));
     data.push_back('\0');
   }
   size_t size(){ return data.size()-1; }
   const char *str()const{return data.data() ;}
private:
 vector<char> data;
 
};
 
int main()
{
    string mama="mama";
    auto find_a= my_sweet_dreams::find(mama.begin(), mama.end(), 'a');
    cout<<*find_a<<" has found at "<<(find_a-mama.begin())<<endl;
    string papa="papa", me="me";
    vector<string>vs{mama, me, papa};
    auto find_me= my_sweet_dreams::find(vs.begin(), vs.end(), "me");
    cout<<*find_me<<" has found at "<<(find_me-vs.begin())<<endl;
 
    Stringer Str("brother");
    for(auto c:Str)cout<<c;
    cout<<endl;
    cout<<Str.str()<<endl;
    auto find_o= my_sweet_dreams::find(Str.begin(), Str.end(), 'o');
    cout<<*find_o<<" has found at "<<(find_o-Str.begin())<<endl;
    find_o= my_sweet_dreams::find(Str.begin(), Str.end(), 'm');
if(find_o==Str.end())cout<<"m not found";
 
    return 0;
}