using System.Windows.Forms;
using System.Drawing;

module Program
{
  Main() : void
  {
    def form               = Form();
    def expressionComboBox = ComboBox();
    def calculateButton    = Button();
    def resultTextBox      = TextBox();
    
    expressionComboBox.TabIndex  = 0;
    expressionComboBox.Bounds    = Rectangle(10, 10, 330, 30);
    
    calculateButton.AutoSize     = true;
    calculateButton.AutoSizeMode = AutoSizeMode.GrowAndShrink;
    calculateButton.TabIndex     = 1;
    calculateButton.Text         = "Calculate";
    calculateButton.Location     = Point(350, 10);
    
    resultTextBox.Location       = Point(10,  40);
    resultTextBox.Width          = calculateButton.Right - 20;
    resultTextBox.TabIndex       = 2;
    
    form.AcceptButton            = calculateButton;
    form.Text                    = "Calculator";

    form.Controls.Add(resultTextBox);
    form.Controls.Add(calculateButton);
    form.Controls.Add(expressionComboBox);

    form.ClientSize = Size(calculateButton.Right + 10, 
                           resultTextBox.Top + resultTextBox.Height + 10);
    
    calculateButton.Click += 
      fun(_, _)
      {
        def text = expressionComboBox.Text;
        def calc = CalcParser();
        
        def updateHistoryList()
        {
          def index = expressionComboBox.Items.IndexOf(text);
          
          when (index >= 0)
          {
            expressionComboBox.Items.RemoveAt(index);
            expressionComboBox.Text = text;
          }
            
          expressionComboBox.Items.Insert(0, text);
        }
        
        updateHistoryList();
        
        match (calc.ParseAndEval(text))
        {
          | Some(val) => resultTextBox.Text = val.ToString();
          | None      =>
            def (pos, msg) = calc.Error;
            
            resultTextBox.Text = msg;
            
            when (pos >= 0)
            {
              expressionComboBox.SelectionStart = pos;
              expressionComboBox.SelectionLength = 1;
              expressionComboBox.Select();
            }
        }
      };
    
    Application.EnableVisualStyles();
    Application.Run(form);
  }
}

Пример должен быть:
* Кратким. Я должен легко описать его в рамках одной статьи (10-15) страниц (по 5 тысяч знаков без учета пробелов).
* Он должен демонстрировать наследование, виртуальные методы, события. Хорошо бы, но не обязательно, чтобы он так же демонстрировал использование интерфейсов.
* Понятным.
* Не абстрактным и практичным. Меня самого всегда раздражало когда ООП подавали на совершенно не реалистичных примерах вроде построения иерархии животных или библиотеки графических примитивов (которые на практике никакого ООП не используют).
* Возможно, но не обязательно, связан с примером строчного калькулятор.

class IDataProcessor
{
 virtual void SendData(std::vector<BYTE> &vData) = 0;
 virtual void ReceiveData(std::vector<BYTE> &vData) = 0;
}

Итак, как для компьютерных, так и для естественных языков справедливо: язык направляет мысли, но не предписывает их.

class Recipe   // Knows its ingredients and quantities
class Product  // Knows its price and recipe
class CashBox         // Knows credit available. Handles money or direct debit.
class ProductSelector // Knows products; Captures selection; Coordinates CashBox and Mixer.
class Mixer           // Interprets recipes; Coordinates dispensers.

class BlackCoffee subclass of Product 
class WhiteCoffee subclass of Product 
class BlackSugarCoffee subclass of Product 
class WhiteSugarCoffee subclass of Product 
class Bouillon subclass of Product 
class Moccha subclass of Product

LCR>class Recipe   // Knows its ingredients and quantities
LCR>class Product  // Knows its price and recipe
LCR>class CashBox         // Knows credit available. Handles money or direct debit.
LCR>class ProductSelector // Knows products; Captures selection; Coordinates CashBox and Mixer.
LCR>class Mixer           // Interprets recipes; Coordinates dispensers.

LCR>class BlackCoffee subclass of Product 
LCR>class WhiteCoffee subclass of Product 
LCR>class BlackSugarCoffee subclass of Product 
LCR>class WhiteSugarCoffee subclass of Product 
LCR>class Bouillon subclass of Product 
LCR>class Moccha subclass of Product
LCR>

class BlackCoffee subclass of Product 
class WhiteCoffee subclass of Product 
class BlackSugarCoffee subclass of Product 
class WhiteSugarCoffee subclass of Product

public int SomeProp {
   get{}

   set {
   ...
      if(_value!=value) {
         ...
         var args = new SomeEventArgs(value);
         if(OnSomePropChanging(args))
            OnSomePropChanged(args);
      }
  }
} 

public event SomeCancelEventHandler SomePropChanging;
public event SomeEventHandler SomePropChanged;

protected virtual bool OnSomePropChanging(...) {
   var callback = SomePropChanging;
   if(callback!=null) {
      bool cancel =  false;
      callback(.., ref cancel);
      return cancel;
   }
   return true;
}
protected virtual void OnSomePropChanged(...) {...}

I> У дядьки вот здесь очень неплохо вышло

About the author

Omar AL Zabir is a student of…

Кто скажет что это девочка пусть первым бросит в меня камень.

He developed the Web-based automation and collaboration system for his university using the .NET Framework almost three years ago when it was in the Beta 1 stage. He has also worked for seven years (beginning when he was in high school) at Orion Technologies as Lead Developer, developing solutions for large banks in the United States. His love for Microsoft technologies can be seen at his Web site www.oazabir.com.

I>

I>He developed the Web-based automation and collaboration system for his university using the .NET Framework almost three years ago when it was in the Beta 1 stage. He has also worked for seven years (beginning when he was in high school) at Orion Technologies as Lead Developer, developing solutions for large banks in the United States. His love for Microsoft technologies can be seen at his Web site www.oazabir.com.

Reactive programming is a programming paradigm oriented around data flows and the propagation of change. This means that it should be possible to express static or dynamic data flows with ease in the programming languages used, and that the underlying execution model will automatically propagate changes through the data flow.

monsters
    .FindNearMonsters(bullet) // отсекаем большую часть живности используя что-то типа quadmap.
    .FlatMap(monster => // Находим всех монстров в которых попадает эта пуля
        do
        {
            dist <- monster.Collide(bullet); // Collide возвращает option (он же maby)
            return (dist, monster);
        })
    .FindBest(((oldDist, _), (newDist, _)) => newDist < oldDist) // Выбераем первого

Reactive programming is a programming paradigm oriented around data flows and the propagation of change.

foreach (bullet in bullets)
{
    do
    {
        (_, monster) <- monsters
            .FindNearMonsters(bullet) // отсекаем большую часть живности используя что-то типа quadmap.
            .FlatMap(monster => // Находим всех монстров в которых попадает эта пуля
                    do
                    {
                            dist <- monster.Collide(bullet); // Collide возвращает option (он же maby)
                            return (dist, monster);
                    })
            .FindBest(((oldDist, _), (newDist, _)) => newDist < oldDist); // Выбераем первого
        def isDead = monster.Hit(bullet); // вот тебе изменение состояния.
        when (isDead)
            monsters.Remove(monster); // вот второе. Убираем мертвых монстров из коллекции.
    }
}