ex17_14_15_16.cpp

/***************************************************************************
 *  @file       main.cpp
 *  @author     Queequeg
 *  @date       19  Nov 2014
 *  @remark     This code is for the exercises from C++ Primer 5th Edition
 *  @note       There are some bugs in gcc(include the latest version 4.9.2) 
 *              to handle regular expression.To compile this program, please
 *			    turn to other compilers such as msvs2013 and clang.
 ***************************************************************************/
//
// Exercise 17.14
// Write several regular expressions designed to trigger various errors.
// Run your program to see what output your compiler generates for each error.

// Exercise 17.15
// Write  a program using the pattern that finds word that violate the
// "i before e except after c" rule. Have your program prompt the user to
// supply a word and indicate whether the word is okay or not. Test your
// program with words that do and do not violate the rule.

// Exercise 17.16
// What would happen if your regex object in the previous program were
// initialized with "[^c]ei"? Test your program using that pattern to see
// whether your expectations were correct.


#include <iostream>
using std::cout;
using std::cin;
using std::endl;

#include <string>
using std::string;

#include <regex>
using std::regex;
using std::regex_error;

int main()
{
    // for ex17.14
    // error_brack
    try{
        regex r("[[:alnum:]+\\.(cpp|cxx|cc)$", regex::icase);
    }
    catch(regex_error e)
    {
        cout << e.what() << " code: " << e.code() << endl;
    }

    // for ex17.15
    regex r("[[:alpha:]]*[^c]ei[[:alpha:]]*", regex::icase);
    string s;
    cout << "Please input a word! Input 'q' to quit!" << endl;
    while(cin >> s && s != "q")
    {
        if(std::regex_match(s, r))
            cout << "Input word " << s << " is okay!" << endl;
        else
            cout << "Input word " << s << " is not okay!" <<endl;

        cout << "Please input a word! Input 'q' to quit!" << endl;
    }

    cout << endl;

    // for ex17.16
    r.assign("[^c]ei", regex::icase);
    cout << "Please input a word! Input 'q' to quit!" << endl;
    while(cin >> s && s != "q")
    {
        if(std::regex_match(s, r))
            cout << "Input word " << s << " is okay!" << endl;
        else
            cout << "Input word " << s << " is not okay!" <<endl;

        cout << "Please input a word! Input 'q' to quit!" << endl;
    }

    return 0;
}