[Valmont]

Bulk operations will benefit from the stream iterators greatly. As it happens to be they behave like a container, so we can use them quite elgantly. They are fast for mass storage/retreival.

Tip:
- Don't forget to overload your extraction/insertion operators. It is crucial as you will obviously see.
- Learn to include the <iterator> header. The standard requires it, yet a only a relative few include them. The fact code often works without the include is bad luck: compiler designers mistake.
- Check out: istreambuf_iterator<> as well.
- Check out: back_insert_iterator<>() as well.

#include <iostream>
#include <vector>
#include <fstream>
#include <string>
#include <iterator>
#include <algorithm>

// istream_iterator, ostream_iterator bulk operations demo.
// 1) We create a file of martian data, by stream a vector towards ostream.
// 2) Then we empty the vector.
// 3) We load the file back into the vector and view its contents.

using namespace std;

//--

struct Martian
{
   int age_;
   bool gender_;
   string species_;
};

//--

ostream& operator<<(ostream& os, const Martian& md)
{
   os<<md.age_<<" "<<md.gender_<<" "<<md.species_;
   return os;
}

//--------------------------------------------------

istream& operator>>(istream& is, Martian& md)
{
  is>>md.age_>>md.gender_;
  //So the species (std::string) name can have spaces.
  getline(is, md.species_);
  return is;
}

//--------------------------------------------------

void save_db(vector<Martian>& mguide)
{
  ofstream outfile("MartianData.txt");
  copy(mguide.begin(), mguide.end(), ostream_iterator<Martian>(outfile, "\n") );
  outfile.close();
}

//--------------------------------------------------

void open_db(vector<Martian>& mguide)
{
  ifstream infile("MartianData.txt");
  copy( istream_iterator<Martian>(infile), istream_iterator<Martian>(),
    back_inserter(mguide) );
  infile.close();
}

//--------------------------------------------------


int main(int argc, char *argv[])
{

  Martian theMd;
  vector<Martian> martianGuide;
  //Let's create some martian info and dump it in a vector.
  theMd.age_ = 320;
  theMd.gender_ = false;
  theMd.species_ = "Crater Planktons";
  martianGuide.push_back(theMd);
  
  theMd.age_ = 243;
  theMd.gender_ = false;
  theMd.species_ = "Mountain Worms";
  martianGuide.push_back(theMd);
  
  theMd.age_ = 211;
  theMd.gender_ = true;
  theMd.species_ = "Sky Fish";
  martianGuide.push_back(theMd);
  
  //Let's save it to a file.
  save_db(martianGuide);
  //Emtpy this vector.
  martianGuide.erase(martianGuide.begin(), martianGuide.end() );
  //Fill the vector again to verify correct storage and operator>> overload.
  open_db(martianGuide);
  
  copy(martianGuide.begin(), martianGuide.end(), ostream_iterator<Martian>(cout, "\n"));

  return 0;
}