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Exercise 23.1; Exercise 23.2
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‎Chapter_23/C23_Exercise_23.1.cpp

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/* Exercise 23.1 */
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#include<iostream>
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#include<istream>
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#include<fstream>
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#include<sstream>
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#include<iomanip>
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#include<string>
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#include<vector>
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#include<map>
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#include"C23_Exercise_23.1.h"
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using namespace std;
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inline void error(string s) { throw runtime_error(s); }
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inline void error(const string& s, const string& s2) { error(s + s2); }
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inline void error(const string& s, int i) { ostringstream os; os << s << ": " << i; error(os.str()); }
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inline void keep_window_open() { char ch; cin >> ch; }
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int main()
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{
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enum Action {
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EXIT = -1, PRINTACTIONLIST,
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CASE1, CASE2, CASE3, CASE4, CASE5
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};
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const string actionList = "\tList of actions:\n"
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" (1) Sender, (2) Recipient\n"
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" (-1) Exit, (0) Print the list of actions\n";
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cout << actionList;
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int action;
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bool cond{ true };
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while (cond) try {
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cout << "\nPlease enter the action: ";
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if (!(cin >> action)) { ClearInput(cin); error("Error. Incorrect input"); }
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char ch;
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cin.get(ch);
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switch (action) {
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case CASE1: {
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cout << endl;
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Mail_file mfile{ "C23_Exercise_23.1_mail.txt" }; // initialize mfile from a file
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// first gather messages from each sender together in a multimap:
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multimap<string, const Message*> sender;
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for (const auto& m : mfile) {
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string s;
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if (find_from_addr(&m, s)) {
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sender.insert(make_pair(s, &m));
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}
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}
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// now iterate through the multimap
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// and extract the subjects of John Doe’s messages:
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auto pp = sender.equal_range("John Doe <jdoe@machine.example>");
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for (auto p = pp.first; p != pp.second; ++p) {
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cout << find_subject(p->second) << '\n';
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}
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cout << vsp_2;
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break;
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}
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case CASE2: {
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cout << endl;
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Mail_file mfile{ "C23_Exercise_23.1_mail.txt" };
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multimap<string, const Message*> recipient;
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for (const auto& m : mfile) {
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string s;
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if (find_to_addr(&m, s)) {
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recipient.insert(make_pair(s, &m));
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}
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}
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// now iterate through the multimap
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// and extract the subjects of John Doe’s messages:
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auto pp = recipient.equal_range("Chester Cole <ccole@example.net>");
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int messageNum = 0;
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for (auto p = pp.first; p != pp.second; ++p) {
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++messageNum;
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cout << sp_2 << "Message #" << messageNum << endl;
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for (auto it = p->second->begin(); it != p->second->end(); ++it) {
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cout << sp_4 << *it << endl;
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}
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cout << endl;
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}
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cout << vsp_2;
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break;
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}
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case PRINTACTIONLIST:
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cout << actionList;
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break;
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case EXIT:
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cond = false;
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break;
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default:
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error("Error. Incorrect action number");
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break;
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}
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}
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catch (runtime_error& e) {
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cerr << e.what() << endl;
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}
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catch (...) {
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cerr << "Error. Exception\n";
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return 1;
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}
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return 0;
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}
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void ClearInput(istream& is)
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{
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is.clear();
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is.ignore(numeric_limits<streamsize>::max(), '\n');
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}
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Mail_file::Mail_file(const string& n)
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// open file named n
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// read the lines from n into lines
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// find the messages in the lines and compose them in m
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// for simplicity assume every message is ended by a ---- line
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{
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ifstream in{ n }; // open the file
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if (!in) {
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cerr << "no " << n << '\n';
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exit(1); // terminate the program
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}
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for (string s; getline(in, s); ) { // build the vector of lines
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lines.push_back(s);
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}
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auto first = lines.begin(); // build the vector of Messages
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for (auto p = lines.begin(); p != lines.end(); ++p) {
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if (*p == "----") { // end of message
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m.push_back(Message(first, p));
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first = p + 1; // ---- not part of message
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}
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}
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}
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int is_prefix(const string& s, const string& p) // is p the first part of s?
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{
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int n = p.size();
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if (string(s, 0, n) == p) return n;
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return 0;
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}
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bool find_from_addr(const Message* m, string& s)
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{
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for (const auto& x : *m) {
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if (int n = is_prefix(x, "From: ")) {
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s = string(x, n);
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return true;
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}
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}
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return false;
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}
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bool find_to_addr(const Message* m, string& s)
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{
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for (const auto& x : *m) {
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if (int n = is_prefix(x, "To: ")) {
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s = string(x, n);
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return true;
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}
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}
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return false;
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}
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string find_subject(const Message* m)
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{
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for (const auto& x : *m) {
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if (int n = is_prefix(x, "Subject: ")) return string(x, n);
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}
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return "";
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}

‎Chapter_23/C23_Exercise_23.1.h

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/* Exercise 23.1 */
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using namespace std;
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const char* sp_2 = " ";
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const char* sp_4 = " ";
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const char* sp_6 = " ";
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const char* sp_8 = " ";
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const char* vsp_2 = "\n\n";
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const char* vsp_3 = "\n\n\n";
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const char* vsp_4 = "\n\n\n\n";
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void ClearInput(istream& is);
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using Line_iter = vector<string>::const_iterator;
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class Message { // a Message points to the first and the last lines of a message
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Line_iter first;
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Line_iter last;
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public:
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Message(Line_iter p1, Line_iter p2) :first{ p1 }, last{ p2 } { }
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Line_iter begin() const { return first; }
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Line_iter end() const { return last; }
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//...
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};
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using Mess_iter = vector<Message>::const_iterator;
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struct Mail_file { // a Mail_file holds all the lines from a file
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// and simplifies access to messages
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string name; // file name
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vector<string> lines; // the lines in order
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vector<Message> m; // Messages in order
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Mail_file(const string& n); // read file n into lines
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Mess_iter begin() const { return m.begin(); }
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Mess_iter end() const { return m.end(); }
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};
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// find the name of the sender in a Message;
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// return true if found
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// if found, place the sender’s name in s:
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bool find_from_addr(const Message* m, string& s);
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bool find_to_addr(const Message* m, string& s);
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// return the subject of the Message, if any, otherwise "":
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string find_subject(const Message* m);

‎Chapter_23/C23_Exercise_23.1_mail.txt

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From: John Doe <jdoe@machine.example>
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To: Mary Smith <mary@example.net>
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Subject: Saying Hello
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Date: 1997年11月21日 09:55:06 -0600
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Message-ID: <1234@local.machine.example>
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This is a message just to say hello.
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So, "Hello".
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----
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From: Mary Smith <mary@example.net>
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To: John Doe <jdoe@machine.example>
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Reply-To: "Mary Smith: Personal Account" <smith@home.example>
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Subject: Re: Saying Hello
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Date: 1997年11月21日 10:01:10 -0600
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Message-ID: <3456@example.net>
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In-Reply-To: <1234@local.machine.example>
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References: <1234@local.machine.example>
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This is a reply to your hello.
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----
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To: "Mary Smith: Personal Account" <smith@home.example>
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From: John Doe <jdoe@machine.example>
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Subject: Re: Saying Hello
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Date: 1997年11月21日 11:00:00 -0600
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Message-ID: <abcd.1234@local.machine.tld>
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In-Reply-To: <3456@example.net>
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References: <1234@local.machine.example> <3456@example.net>
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This is a reply to your reply.
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----
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From: John Doe <jdoe@machine.example>
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To: Chester Cole <ccole@example.net>
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Subject: Hello to Chester
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Date: 1997年11月23日 09:00:06 -0600
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Message-ID: <5555@local.machine.example>
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One more "Hello".
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----
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From: John Doe <jdoe@machine.example>
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To: Eli Harris <eharris@example.net>
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Subject: Hello to Eli
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Date: 1997年11月23日 09:01:15 -0600
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Message-ID: <6666@local.machine.example>
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One more "Hello".
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----
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From: Mary Smith <mary@example.net>
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To: Chester Cole <ccole@example.net>
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Subject: Business proposal
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Date: 1997年11月25日 10:36:19 -0600
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Message-ID: <3478@example.net>
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Good morning, Chester
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I have a business proposal for you
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----

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