An iterator that casts the input data to another type. Note: std::transform should probably be used in most cases

ostream_cast_iterator.cpp

#include <iostream>
#include <map>
#include <sstream>
#include <string>
#include <iterator>

template <class T, class C, class charT=char, class traits=std::char_traits<charT> >
class ostream_cast_iterator :
    public std::iterator<std::output_iterator_tag, void, void, void, void>
{
    std::basic_ostream<charT,traits>* out_stream;
    const charT* delim;

public:
    typedef charT char_type;
    typedef traits traits_type;
    typedef std::basic_ostream<charT,traits> ostream_type;
    ostream_cast_iterator(ostream_type& s) : out_stream(&s), delim(0) {}
    ostream_cast_iterator(ostream_type& s, const charT* delimiter)
        : out_stream(&s), delim(delimiter) { }
    ostream_cast_iterator(const ostream_cast_iterator<T,C,charT,traits>& x)
        : out_stream(x.out_stream), delim(x.delim) {}
    ~ostream_cast_iterator() {}

    ostream_cast_iterator<T,C,charT,traits>& operator= (const T& value) {
        *out_stream << C(value);
        if (delim!=0) *out_stream << delim;
        return *this;
    }

    ostream_cast_iterator<T,C,charT,traits>& operator*() { return *this; }
    ostream_cast_iterator<T,C,charT,traits>& operator++() { return *this; }
    ostream_cast_iterator<T,C,charT,traits>& operator++(int) { return *this; }
};

class PairToString {
public:
    template<typename T>
    PairToString(const T & thePair) {
        std::stringstream ss;
        ss << thePair.first << ": " << thePair.second;
        convertedPair = ss.str();
    }

    operator std::string() const {
        return convertedPair;
    }

private:
    std::string convertedPair;
};

int main() {
    std::map<std::string, int> persons;
    persons["Peter"] = 34;
    persons["Katten"] = 88;
    persons["Hatten"] = 2353;
    persons["Reagan"] = 1337;

    std::copy(persons.begin(), persons.end(), ostream_cast_iterator<PairToString, std::string>(std::cout, "\n"));
}