HQ9F+.cpp

#include <iostream>
#include <fstream>
#include <string>
#include <cctype>
#include <vector>

using namespace std;

void printH()
{
    cout << "Hello, world!" << endl;
}

void printQ(vector<string> buffer)
{
    for (auto v : buffer) cout << v << endl;
}

void print9()
{
    cout << "99 bottles of beer on the wall, 99 bottles of beer." << endl;
    for (int i = 98; i > 1; --i)
    {
        cout << "Take one down and pass it around, " << i << " bottles of beer on the wall." << endl << endl;
        cout << i << "bottles of beer on the wall, " << i << "bottles of beer." << endl;
    }
    cout << "Take one down and pass it around, 1 bottle of beer on the wall." << endl << endl;
    cout << "1 bottle of beer on the wall, 1 bottle of beer." << endl;
    cout << "Take one down and pass it around, no more bottles of beer on the wall." << endl << endl;
    cout << "No more bottles of beer on the wall, no more bottles of beer." << endl;
    cout << "Go to the store and buy some more, 99 bottles of beer on the wall." << endl;
}

void printF()
{
    for (int i = 1; i <= 100; ++i)
    {
        if (i % 3  == 0) cout << "Fizz";
        if (i % 5  == 0) cout << "Buzz";
        if (i % 3 != 0 && i % 5 != 0) cout << i;
        cout << endl;
    }
}

void printHelp()
{
    cout << "This is an interpreter of HQ9F+." << endl;
    cout << "HQ9F+ is a joke programming language. It has four operations." << endl;
    cout << " -- H: print \"Hello, world!\"" << endl;
    cout << " -- Q: print the program's source code (sometimes called a quine)" << endl;
    cout << " -- 9: print the lyrics to 99 Bottles of Beer" << endl;
    cout << " -- F: print the fizzbuzz to 100 from 1" << endl;
    cout << " -- +: add one to the accumulator (the value of the accumulator cannot be accessed)" << endl;

}

void printVersion()
{
    cout << "Version: 1.0" << endl;
}

int main(int argc, char **argv)
{
    if (argc < 2)
    {
        printHelp();
        printVersion();
    }
    else
    {
        ifstream ifs(argv[1]);
        if (ifs.fail())   // fail : file not found
        {
            cerr << "Cannot open the file: \"" << argv[1] << "\"" << endl;
            return 1;
        }

        int accumulator = 0;
        vector<string> buffer;
        string buf;
        while (getline(ifs, buf, '\n')) buffer.push_back(buf);

        for (int i = 0; i < buffer.size(); ++i)
        {
            int length = buffer[i].length();
            for (int j = 0; j < length; ++j)
            {
                switch (toupper(buffer[i][j]))
                {
                    case 'H':
                        printH();
                        break;
                    case 'Q':
                        printQ(buffer);
                        break;
                    case '9':
                        print9();
                        break;
                    case 'F':
                        printF();
                    case '+':
                        ++accumulator;
                        break;
                    default:
                        cerr << "undefined token : " << "\'" << buffer[i] << "\' (line: " << i + 1 << ", " << j + 1 << ")" << endl;
                        return 1;
                }
            }
        }
        ifs.close();
    }
}