Ceylon: Introduction to classes

	class ImmutablePerson1(firstName, lastName) {
	shared String firstName;
	shared String lastName;
	//below we override the super method Object.string which has a default implementation
	shared actual String string => "Person(``firstName`` ``lastName``)";
	}
	/**
	this is shortcut syntax but this is not the preferred way when you have more than
	2 class parameters (constructor parameters)
	**/
	class ImmutablePerson2(shared String firstName, shared String lastName) {
	}
	/**
	We can mutate firstName and lastName of instances of MutablePerson
	**/
	class MutablePerson(firstName, lastName) {
	shared variable String firstName;
	shared variable String lastName;
	shared actual String string => "Person(``firstName`` ``lastName``)";
	}
	/**
	We can even give default values to class parameters
	**/
	class DefaultPerson(firstName, shared String lastName="Pelssers") {
	shared String firstName;
	shared actual String string => "Person(``firstName`` ``lastName``)";
	}
	/**
	The main method prints
	*******************
	Person(Robby Pelssers)
	Robby
	*******************
	com.pelssers.demo.ImmutablePerson2@4400dfe4
	Davy
	*******************
	Person(Lindsey Pelssers)
	Lindsey
	*******************
	Person(Valerie Pelssers)
	Valerie
	*******************
	Person(Jef Pelssers)
	Jef
	*******************
	**/
	void main() {
	print("*******************");
	ImmutablePerson1 person1 = ImmutablePerson1("Robby", "Pelssers");
	print(person1);
	//person.firstName = "Davy"; WON'T COMPILE
	print(person1.firstName);
	print("*******************");
	ImmutablePerson2 person2 = ImmutablePerson2("Davy", "Pelssers");
	print(person2);
	print(person2.firstName);
	print("*******************");
	MutablePerson person3 = MutablePerson("Lindsey", "Pelssers");
	print(person3);
	print(person3.firstName);
	print("*******************");
	person3.firstName = "Valerie";
	print(person3);
	print(person3.firstName);
	print("*******************");
	DefaultPerson person4 = DefaultPerson("Jef");
	print(person4);
	print(person4.firstName);
	print("*******************");
	}

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	/**
	Below an example of how to extend other classes.
	Mammal has a default implementation for eating.
	Lion does not override eat() whereas
	Squirrel provides it's own implementation.
	**/
	class Mammal(shared String name="Mammal") {
	shared default void eat() {
	print("``name`` eating food.");
	}
	}
	class Lion() extends Mammal("Lion") {
	}
	class Squirrel() extends Mammal("Squirrel") {
	//here we override the default implementation
	shared actual void eat() {
	print("``name`` eating nuts.");
	}
	}
	class Cat() extends Mammal("Cat") {
	//shortcut notation to refine (override) a default implementation
	eat() => print("``name`` eating mouse.");
	}
	/**
	the demo prints the following to the console:
	Some mammal eating food.
	Lion eating food.
	Squirrel eating nuts.
	Cat eating mouse.
	**/
	void inheritance_demo() {
	Mammal mammal = Mammal("Some mammal");
	mammal.eat();
	Lion lion = Lion();
	lion.eat();
	Squirrel squirrel = Squirrel();
	squirrel.eat();
	Cat cat = Cat();
	cat.eat();
	}

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	abstract class Shape(name) {
	shared String name;
	shared formal Float circumference();
	shared formal Float area();
	shared actual String string => "``name`` with circumference=``circumference()``
	and area=``area()``".normalized;
	}
	class Rectangle(Float width, Float length) extends Shape("Rectangle") {
	circumference() => 2 * width + 2 * length;
	area() => width * length;
	}
	/**
	Running this program prints :
	Rectangle with circumference=70.0 and area=300.0
	**/
	void abstractclass_demo() {
	Rectangle rect = Rectangle(15.0, 20.0);
	print(rect);
	}

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