Sina's assigment

#include <fstream>
// using std::ofstream, std::ifstream
#include <iostream>
// using std::cerr
#include <string>
// using std::string

int main()
{
  std::ifstream emails("mail.dat");
  std::ofstream addresses("addresses.dat");
  if(! (emails && addresses)) {
    std::cerr << "Error opening" << std::endl;
    return 1;
  }
  for(std::string word; emails >> word; ) {
    if(word.find('@') == std::string::npos)
      continue; // not a mail
    std::string::size_type last_n = word.length() - 1;
    char last = word[last_n];
    if(last == '>' || last == ',')
      word.erase(last_n);
    if(word[0] == '<')
      word.erase(0, 1);
    if(! (addresses << word).put('\n')) {
      std::cerr << "Error writing" << std::endl;
      return 1;
    }
  }
  return 0;
}