Single most complicated "Hello World" program

[Need4Sleep]

Lets see who is the most creative!
RULES:
[]No third party lib's(SFML,Allegro..etc..etc)
[]Length does not factor in, writing 10000 functions that connect and end with calling "hello world" is not creative, it's repetitive.
[]Describe your program above

Ill start:

I used: Inheritance and dynamic allocation

#include <iostream>

class AbstractHello
{
    public:
        virtual ~AbstractHello(){std::cout << " World!";}
        void Prnt(){std::cout << "Hello";}


};

class ChildHello: public AbstractHello
{
    public:
        ~ChildHello(){Prnt();}
};

int main()
{
    ChildHello *Obj;
    Obj = new ChildHello;
    delete Obj;
}

[Catfish2]

Classic mistake in such threads... OP forgets to force a language. inb4 assembly.

Anyway. My usual candidate:

#include <iostream>

int main()
{
    return static_cast<int> (static_cast<bool> (std::endl(operator<<(std::cout, "Hello, World!"))));
}

[Duthomhas]

Didn't we just have one of these threads?

[htirwin]

#include <iostream>

int main() {
    int n = 0;
    again:
    for (int i = n == 0 ? 'H' : n == 1 ? 'E' : (n == 2 || n == 3 ) ? 'L' : n == 4 ? 'O' : 0; i ; ) {
        std::cout << (char)i;
        ++n;
        if (i) {
            goto again;
        }
    }
    return 0;
}

[andywestken]

Well, I obviously have spent too much time in Internet cafes waiting for trains...

This solution took its initial inspiration from Need4Sleep's Inheritance-and-dynamic-allocation version above. After a quick Google, I realised no one has really taken the Hello world program seriously. So I built on Need4Sleep's version after performing a brief OOA/D and applying a few patterns.

Note that this is only prototype. It has not been reviewed yet, and needs error handling and localization applied to it. Plus full unit testing. It should be able to reduce the amount of code a bit, without sacrificing extensibility, by additional use of templating.

The analysis revealed that a message is, in general, a sequence of sentences. A sentence a sequence of words. A word a sequence of words. And, finally, a word a sequence of letters. This suggests the composite pattern. Etc.

Even though it was not fully specified, I took it as read that as this is a C++ forum that I should stick to platform agnostic ANSI C++.

/*!
 * Hello world! application
 * 
 * \file hello.cpp
 */

#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>
#include <cassert>

/*!
 * Dispay message.
 */
void displayMessage();

/*!
 * Sentence type
 *
 * Type of sentence, used to decide how to terminate sentence.
 */
enum ESentenceType {
    eStatement,
    eExclamation,
    sQuestion,
    eCommand
};

/*!
 * Utility class to prevent unintended copying of class instances.
 */
class nonCopyable {
protected:
    nonCopyable() {
    }

    ~nonCopyable() {
    }

private:
    nonCopyable(const nonCopyable&);
    const nonCopyable& operator=(const nonCopyable&);
};

/*!
 * Utility function to obtain punctuation mark to end sentence
 * of specified type.
 */
inline char getPunctionMark(ESentenceType sentenceType) {
    char puncMark = '.';
    switch(sentenceType) {
        case eStatement  : puncMark = '.'; break;
        case eExclamation: puncMark = '!'; break;
        case sQuestion   : puncMark = '?'; break;
        case eCommand    : puncMark = '.'; break;
        default: {
            // should never get here
            assert(false);
        }
    }
    return puncMark;
}

/*!
 * Utility class for creation of instances.
 */
template<typename TElem>
class Creatable {
protected:
    Creatable() {
    }

    virtual ~Creatable() {
        clear();
    }

public:
    static TElem* create() {
        TElem* e = new TElem;
        return e;
    }

    void free() {
        delete this;
    }

    virtual void clear() {
    }
};

template<typename TElem, typename TParam>
class CreatableParam {
protected:
    CreatableParam() {
    }

    virtual ~CreatableParam() {
    }

public:
    static TElem* create(TParam p) {
        TElem* e = new TElem;
        e->initialize(p);
        return e;
    }

    void free() {
        finalize();
        delete this;
    }

    virtual void initialize(TParam /*p*/) {
    }

    virtual void finalize() {
        clear();
    }

    virtual void clear() {
    }
};

/*!
 * Base class for displayable content
 */
class DisplayElem
: public nonCopyable {
protected:
    DisplayElem() {
    }

    virtual ~DisplayElem() {
    }

public:
    virtual void display(std::ostream& os) const = 0;
};

/*!
 * STL algorithm for displaying elements
 */
class Displayer
: public std::unary_function<void, const DisplayElem*> {
private:
    std::ostream& m_os;
    char   m_sep;
    size_t m_count;

public:
    Displayer(std::ostream& os, char sep = '\0')
    : m_os(os)
    , m_sep(sep)
    , m_count(0) {
    }

    ~Displayer() {
    }

    void operator()(const DisplayElem* e) {
        if(('\0' != m_sep) && (0 < m_count)) {
            m_os << m_sep;
        }
        e->display(m_os);
        ++m_count;
    }
};

/*!
 * STL algorithm for freeing display elements
 */
template <typename TElem>
class Freer
: public std::unary_function<void, TElem*> {
public:
    void operator()(TElem* e) {
        e->free();
    }
};

/*!
 * Display element for letter.
 *
 * The letter is the fundamental element: it has no substructure.
 */
class Letter
: public DisplayElem
, public CreatableParam<Letter, char> {
private:
    char m_ch;

protected:
    /*virtual*/ ~Letter() {
    }

public:
    Letter() : m_ch('\0') {
    }

    void initialize(char ch) {
        m_ch = ch;
    }

    void finalize() {
        m_ch = '\0';
    }

    void display(std::ostream& os) const {
        os << m_ch;
        // no endLetter()
    }
};

/*!
 * Display element for word.
 *
 * A word is a sequence of letters.
 */
class Word
: public DisplayElem
, public Creatable<Word> {
private:
    std::vector<Letter*> m_letters;

protected:
    /*virtual*/ ~Word() {
        clear();
    }

public:
    Word() {
    }

    void clear() {
        std::for_each(m_letters.begin(), m_letters.end(), Freer<Letter>());
        m_letters.clear();
    }

    void addLetter(Letter* s) {
        m_letters.push_back(s);
    }

    /*virtual*/ void display(std::ostream& os) const {
        std::for_each(m_letters.begin(), m_letters.end(), Displayer(os));
        // no endLetter()
    }
};

/*!
 * Display element for sentence.
 *
 * A sentence is a sequence of words.
 */
class Sentence
: public DisplayElem
, public CreatableParam<Sentence, ESentenceType> {
private:
    std::vector<Word*> m_words;

    ESentenceType m_sentenceType;

protected:
    /*virtual*/ ~Sentence() {
        clear();
    }

    void endSentence(std::ostream& os) const {
        const char puncMark = getPunctionMark(m_sentenceType);
        os << puncMark;
    }

public:
    Sentence()
    : m_sentenceType(eStatement) {
    }

    void initialize(ESentenceType sentenceType) {
        m_sentenceType = sentenceType;
    }

    void finalize() {
        m_sentenceType = eStatement;
    }

    void clear() {
        std::for_each(m_words.begin(), m_words.end(), Freer<Word>());
        m_words.clear();
    }

    void addWord(Word* w) {
        m_words.push_back(w);
    }

    void display(std::ostream& os) const {
        std::for_each(m_words.begin(), m_words.end(), Displayer(os, ' '));
        endSentence(os);
    }
};

/*!
 * Display element for message.
 *
 * A message is a sequence of sentences.
 */
class Message
: public DisplayElem
, public Creatable<Message> {
private:
    std::vector<Sentence*> m_sentences;

protected:
    /*virtual*/ ~Message() {
        clear();
    }

    void endMessage(std::ostream& os) const {
        os << std::endl;
    }

public:
    Message() {
    }

    void clear() {
        std::for_each(m_sentences.begin(), m_sentences.end(), Freer<Sentence>());
        m_sentences.clear();
    }

    void addSentence(Sentence* s) {
        m_sentences.push_back(s);
    }

    void display(std::ostream& os) const {
        std::for_each(m_sentences.begin(), m_sentences.end(), Displayer(os, ' '));
        endMessage(os);
    }
};

/*!
 * Main entrance point.
 */
int main() {
    displayMessage();
    return 0;
}

/*!
 * Display message.
 */
void displayMessage() {
    Word* first_word = Word::create();
    first_word->addLetter(Letter::create('H'));
    first_word->addLetter(Letter::create('e'));
    first_word->addLetter(Letter::create('l'));
    first_word->addLetter(Letter::create('l'));
    first_word->addLetter(Letter::create('o'));

    Word* second_word = Word::create();
    second_word->addLetter(Letter::create('w'));
    second_word->addLetter(Letter::create('o'));
    second_word->addLetter(Letter::create('r'));
    second_word->addLetter(Letter::create('l'));
    second_word->addLetter(Letter::create('d'));

    Sentence* sentence = Sentence::create(eExclamation);
    sentence->addWord(first_word);
    sentence->addWord(second_word);

    Message* message = Message::create();
    message->addSentence(sentence);

    message->display(std::cout);

    message->free();
    // sentences, etc freed by parent
}

Microsoft Visual Studio 9.0 (2008)

Hello world!
Press any key to continue . . .

gcc (GCC) 4.4.0

Hello world!

Press any key to continue.

[andywestken]

I have been wandering round the web, looking at other overly complicated versions of Hello world (in assorted languages). Amongst them, I found one page which might actually be of some use to people who are new to design patterns:

Demystifying design patterns
http://calumgrant.net/patterns/index.html

(hello world's based on each of the Gang of Four patterns)

And then there's this Java monstrosity!

The Abuse of Design Patterns in writing a Hello World Program
http://taskinoor.wordpress.com/2011/09/21/the-abuse-of-design-patterns-in-writing-a-hello-world-program/

Andy

[LB]

http://www.cplusplus.com/forum/lounge/41739/