Demonstration of some of the string functions in the Standard C++ string class

//---------------------------------------------------------------
// File: CPPStringDemo.cpp
// Purpose: Demonstration of string functions available through
//        the string string class in C++.
// Programming Language: C++
// Author: Dr. Rick Coleman
//---------------------------------------------------------------
#include <iostream> // Note: This program won't work if you use <iostream.h>
#include <string>

using std::string;
using std::cout;
using std::cin;

int main(int argc, char **argv)
{
    string line;  // Declare a string for demo purposes
                       // Note the addition of "std::" to get the
                       // definition of string from the standard (std)
                       // namespace.
    const char *cStr;   // Used to demonstrate c_str() function.  See below
    char    cArray[128];

    cout << "======================================================================\n";
    cout << "Demonstrating copying the string \"This is a test string.\" into the\n";
    cout << "     instance of the string class str.  This demonstration uses the\n";
    cout << "     overloaded equals operator (=)\n";
    cout << "----------------------------------------------------------------------\n\n";
    // Copy the string using the overloaded operator=
    line = "This is a test string.";
    // Print the results
    cout << "line: " << line << "\n";
    // Also print the length of the string using strlen()
    cout << "Using line.length() Length = " << line.length() << "\n";
    cout << "Using line.size() Length = " << line.size() << "\n";

    cout << "\n\n++++++++++ Press [Enter] to continue. ++++++++++\n\n";
    cin.get();
    cout << "----------------------------------------------------------------------\n\n\n\n";

    cout << "======================================================================\n";
    cout << "Demonstrating concatenating the string \"  It uses string functions.\"\n";
    cout << "     onto the string line. This demonstration uses the overloaded\n";
    cout << "     plus-equals operator (+=)\n";
    cout << "----------------------------------------------------------------------\n\n";
    // Copy the string using strcpy
    line += "  It uses string functions.";
    // Print the results
    cout << "line: " << line << "\n";
    // Print the new length
    cout << "Length = " << line.length() << "\n";

    cout << "\n\n++++++++++ Press [Enter] to continue. ++++++++++\n\n";
    cin.get();
    cout << "----------------------------------------------------------------------\n\n\n\n";

    cout << "======================================================================\n";
    cout << "Demonstrating comparing the string using the overloaded operators\n";
    cout << "     operator== (equals), operator< (does string come alphabetically before)\n";
    cout << "     and operator> (does string come alphabetically after)\n";
    cout << "----------------------------------------------------------------------\n\n";
    cout << "Copying \"MNOP\" into line\n\n";
    line = "MNOP";
    // Compare line to 3 other strings with the == operator. 
    //    One string comes alphabetically before, one is equal, and one comes 
    //    alphabetically after
    cout << "Comparing \"MNOP\" to the string \"ABCD\" with (line == \"ABCD\").  ";
    if(line == "ABCD")
        cout << "\tresults = true\n";
    else
        cout << "\tresults = false\n";

    cout << "Comparing \"MNOP\" to the string \"MNOP\" with (line == \"MNOP\").  ";
    if(line == "MNOP")
        cout << "\tresults = true\n";
    else
        cout << "\tresults = false\n";

    cout << "Comparing \"MNOP\" to the string \"WXYZ\" with (line == \"WXYZ\").  ";
    if(line == "WXYZ")
        cout << "\tresults = true\n\n";
    else
        cout << "\tresults = false\n\n";

    // Compare line to 3 other strings with the > operator. 
    //    One string comes alphabetically before, one is equal, and one comes alphabetically after
    cout << "Comparing \"MNOP\" to the string \"ABCD\" with (line > \"ABCD\").  ";
    if(line > "ABCD")
        cout << "\tresults = true\n";
    else
        cout << "\tresults = false\n";

    cout << "Comparing \"MNOP\" to the string \"MNOP\" with (line > \"MNOP\").  ";
    if(line > "MNOP")
        cout << "\tresults = true\n";
    else
        cout << "\tresults = false\n";

    cout << "Comparing \"MNOP\" to the string \"WXYZ\" with (line > \"WXYZ\").  ";
    if(line > "WXYZ")
        cout << "\tresults = true\n\n";
    else
        cout << "\tresults = false\n\n";

    // Compare line to 3 other strings with the < operator. 
    //    One string comes alphabetically before, one is equal, and one comes alphabetically after
    cout << "Comparing \"MNOP\" to the string \"ABCD\" with (line < \"ABCD\").  ";
    if(line < "ABCD")
        cout << "\tresults = true\n";
    else
        cout << "\tresults = false\n";

    cout << "Comparing \"MNOP\" to the string \"MNOP\" with (line < \"MNOP\").  ";
    if(line < "MNOP")
        cout << "\tresults = true\n";
    else
        cout << "\tresults = false\n";

    cout << "Comparing \"MNOP\" to the string \"WXYZ\" with (line < \"WXYZ\").  ";
    if(line < "WXYZ")
        cout << "\tresults = true\n\n";
    else
        cout << "\tresults = false\n\n";

    cout << "\n\n++++++++++ Press [Enter] to continue. ++++++++++\n\n";
    cin.get();
    cout << "----------------------------------------------------------------------\n\n\n\n";

    cout << "======================================================================\n";
    cout << "\n\nDemonstrating other string functions\n";
    cout << "----------------------------------------------------------------------\n\n";
    cout << "Copying the string \"How do I program thee. Let me iterate the ways.\"";
    cout << " into line.\n\n";
    line = "How do I program thee. Let me iterate the ways.";

    // These have an oops!  Finds first occurance of any of the letters in the string

    cout << "\n\n";
    cout << "======================================================================\n";
    cout << "Demonstrating the function find() used to find the first occurance of\n";
    cout << "     a substring in a given string. This function returns the index in\n";
    cout << "     the string where the search string was found, or -1 if not found.\n";
    cout << "----------------------------------------------------------------------\n\n";
    cout << "Results of call to line.(\"I\") = " << line.find("I") << 
        "\n";
    cout << "To print the string starting from that point use:\n";
    cout << "\t cout << line.substr(line.find(\"I\"), line.length());\n\n";
    cout << "\t Results = " << line.substr(line.find("I"), line.length()) << 
        "\n\n";

    cout << "Results of call to line.find(\"the\") = " << 
        line.find("the") << "\n";
    cout << "To print the string starting from that point use:\n";
    cout << "\t cout << line.substr(line.find(\"the\"), line.length());\n\n";
    cout << "\t Results = " << line.substr(line.find("the"), line.length()) << 
        "\n\n";

    int pos = line.find("love");
    cout << "Results of call to line.find(\"love\") = " << pos << "\n";
    // FYI: If you try to print thr results of the call to find when searching for a
    //    string that is not found cout will print the returned index as an unsigned
    //  int. That means instead of printing the correct -1 it will print 4294967295

    cout << "\n\n++++++++++ Press [Enter] to continue. ++++++++++\n\n";
    cin.get();
    cout << "----------------------------------------------------------------------\n\n\n\n";

    cout << "\n\n";
    cout << "======================================================================\n";
    cout << "Demonstrating the function rfind() used to find the last occurance of\n";
    cout << "     a substring in a given string. This function returns the index in\n";
    cout << "     the string where the search string was found, or -1 if not found.\n";
    cout << "----------------------------------------------------------------------\n\n";
    cout << "Results of call to line.rfind(\"L\") = " << line.rfind("L") << 
        "\n";
    cout << "To print the string starting from that point use:\n";
    cout << "\t cout << line.substr(line.rfind(\"L\"), line.length());\n\n";
    cout << "\t Results = " << line.substr(line.rfind("L"), line.length()) << "\n\n";


    cout << "Results of call to line.rfind(\"the\") = " << 
        line.rfind("the") << "\n";
    cout << "To print the string starting from that point use:\n";
    cout << "\t cout << line.substr(line.rfind(\"the\"), line.length());\n\n";
    cout << "\t Results = " << line.substr(line.rfind("the"), line.length()) << 
        "\n\n";

    pos = line.rfind("love");
    cout << "Results of call to line.rfind(\"love\") = " << pos << "\n";
    // FYI: If you try to print thr results of the call to find when searching for a
    //    string that is not found cout will print the returned index as an unsigned
    //  int. That means instead of printing the correct -1 it will print 4294967295

    cout << "\n\n++++++++++ Press [Enter] to continue. ++++++++++\n\n";
    cin.get();
    cout << "----------------------------------------------------------------------\n\n\n\n";

    cout << "======================================================================\n";
    cout << "\n\nDemonstrating the copying of the contents of a string class \n";
    cout << "into a char array using the command cStr = line.c_str().\n";
    cout << "The variable cStr must be declared as const char *cStr;  Memory is \n";
    cout << "dynamically allocated for the new character and the pointer set point to it.\n";
    cout << "Warning: potential memory leak if you set cStr pointing to something else.\n\n";
    cout << "----------------------------------------------------------------------\n\n";

    cStr = line.c_str();
    cout << "const char *cStr = " << cStr << "\n\n";

    cout << "\n\n++++++++++ Press [Enter] to continue. ++++++++++\n\n";
    cin.get();
    cout << "----------------------------------------------------------------------\n\n\n\n";

    cout << "======================================================================\n";
    cout << "\n\nDemonstrating the copying of the contents of a string class \n";
    cout << "into a char array using the command line.copy(cArray, line.length()).\n";
    cout << "The variable cArray is declared as char cArray[128];\n";
    cout << "Warning: This copy function DOES NOT ADD THE NULL TERMINATOR.\n";
    cout << "To use cArray as a C style string you must add the null terminator\n";
    cout << "like this:  cArray[line.length()] = '\\0';\n\n";
    cout << "----------------------------------------------------------------------\n\n";

    line.copy(cArray, line.length());
    cArray[line.length()] = '\0';
    cout << "Char array cArray = " << cArray << "\n\n";

    cout << "\n\n++++++++++ Press [Enter] to continue. ++++++++++\n\n";
    cin.get();
    cout << "----------------------------------------------------------------------\n\n\n\n";


    return 0;
}