/* Code for exercise 21.2. |  | "C++ Solutions--Companion to The C++ Programming Language, Third Edition" | by David Vandevoorde; Addison-Wesley 1998; ISBN 0-201-30965-3. | | Permission to use, copy, modify, distribute and sell this software | and its documentation for any purpose is hereby granted without fee. | The author makes no representations about the suitability of this | software for any purpose.  It is provided "as is" without express or | implied warranty. `----------------------------------------------------------------------*/#include <fstream>#include <iostream>#include <stdlib.h>#include <string>enum FieldType { kName = 0, kFamilyName = 0, kGivenNames = 1,                 kStreet = 2, kStreetAddress = 2, kCity = 3,                 kCityAndZip = 3, kCountry = 4 };struct Name_and_address {   Name_and_address() {}   Name_and_address(std::string const &name, std::string const &given_names,                    std::string const &street,                    std::string const &city, std::string const &country) {      field_[kName] = name;      field_[kGivenNames] = given_names;      field_[kStreetAddress] = street;      field_[kCityAndZip] = city;      field_[kCountry] = country;   }   void set_field(FieldType f, std::string const &field_value) {      field_[f] = field_value;   }   std::string const& field(FieldType f) const {      return field_[f];   }private:   std::string field_[5];};std::ostream& operator<<(std::ostream &output, Name_and_address const &obj) {   for (int k = kName; k!=kCountry+1; ++k)      output << obj.field(FieldType(k)) << '\n';   return output;};std::istream& operator>>(std::istream &input, Name_and_address &obj) {   for (int k = kName; k!=kCountry+1; ++k) {      std::string line;      std::getline(input, line);      obj.set_field(FieldType(k), line);   }   return input;}void error(char const *prog, char const *entity, char const *msg) {   std::cerr << prog << ": " << entity << msg << '\n';   exit(1);}int main(int argc, char *argv[]) {   if (argc!=3)      error(argv[0], "", ": unexpected number of arguments.");   std::ifstream input(argv[1]);   if (!input)      error(argv[0], argv[1], ": cannot open file for reading.");   std::ofstream output(argv[2]);   if (!output)      error(argv[0], argv[2], ": cannot open file for writing.");   std::copy(std::istream_iterator<Name_and_address, char>(input),             std::istream_iterator<Name_and_address, char>(),             std::ostream_iterator<Name_and_address, char>(output));   return 0;}