added lesson 7

README.md

@@ -57,13 +57,6 @@
 [Files](src/Lesson5)
 - Lists
 - High order functions
-- 
-### Lesson 6 - Tuples and comprehensions
-[Files](src/Lesson6)
-- Tuples
-- For-comprehension
-- Yield
-- Flatmap
 
 ### Midterm preparation
 [Files](src/MidTermPrep1)
@@ -71,6 +64,20 @@
 ### Midterm
 [Files](src/MidTerm1)
 
+### Lesson 6 - Tuples and comprehensions
+[Files](src/Lesson6)
+- Tuples
+- For-comprehension
+- Yield
+- Flatmap
+
+### Lesson 7 - Advanced typing and infinite lists
+[Files](src/Lesson7)
+- Types
+- Bounds
+- Traits
+- Variance, covariance and contra-variance
+- Infinite sequences
 
 ## Assignments
 
@@ -106,3 +113,8 @@
 - Map
 - Fold
 - Zip
+
+### Assignment 6 - Sequence comprehension and tuples
+[Files](src/Assignment6)
+- Tuples
+- `for` comprehension

src/Lesson7/Daltons.sc

@@ -0,0 +1,12 @@
+case class Dalton(n: Int) extends Ordered[Dalton] {
+  //override def compare(that: Dalton): Int = this.n compare that.n
+  override def compare(that: Dalton): Int = this.n - that.n
+}
+
+val a = Dalton(2); val b = Dalton(3); val c = Dalton(2)
+
+a < b
+a > b
+a == b
+a == c
+a >= c

src/Lesson7/LazyEvaluation.sc

@@ -0,0 +1,6 @@
+val expr = {
+  val x = {print("x"); 1}
+  lazy val y = {print("y"); 2}
+  def z = {print("z"); 3}
+  z + y + x + z + y + x
+}

src/Lesson7/LazyList.sc

@@ -0,0 +1,11 @@
+def range(low: Int, high: Int): LazyList[Int] = {
+  println(s"Calling range with low=$low / high=$high")
+  if (low >= high) LazyList.empty[Int]
+  else low #:: range(low + 1, high)
+}
+
+range(1, 10)(0)
+
+range(1, 10) map (x => x + 1)
+
+(range(1, 10) map (x => x + 1)).toList

src/Lesson7/LoggingFactory.sc

@@ -0,0 +1,16 @@
+trait Logged {
+  def log(msg: String)
+}
+
+trait ConsoleLogger extends Logged {
+  override def log(msg: String) = println("[LOG] " + msg)
+}
+
+abstract class Person(name: String)
+
+class Customer(n: String) extends Person(n) with Logged {
+  log(s"Person $n created")
+}
+
+val a = new Customer("Patrick Jane") with ConsoleLogger
+

src/Lesson7/Variance.sc

@@ -0,0 +1,25 @@
+class Animal(val name: String, val kind: String)
+class Cat(name: String) extends Animal(name, "Cat")
+class Dog(name: String) extends Animal(name, "Dog")
+
+val anim1: Animal = new Animal("Booboo", "Baboon")
+val cat1 = new Cat("Miaou")
+
+// Standard polymorphism
+val anim2: Animal = cat1
+
+val dog1: Dog = new Dog("Choucroute")
+val anim3: Animal = dog1
+
+class Container[+A](val elems: List[A]) {
+  def get(i: Int): A = elems(i)
+  def put[B >: A](elem: B) = new Container(elem::elems)
+}
+
+val animalCollection = new Container[Animal](Nil).put(anim1)
+
+val catCollection = new Container[Cat](Nil).put(cat1).put(new Cat("Garfield"))
+
+animalCollection.put(cat1)
+
+val animalCollection2: Container[Animal] = catCollection

src/MidTermPrep1/Exercices.sc

@@ -0,0 +1,8 @@
+def compress[T](list: List[T]): List[T] = {
+  list.foldRight(List.empty[T])((elmt: T, res: List[T]) => res match {
+    case head::_ if head == elmt => res
+    case _ => elmt::res
+  })
+}
+
+compress(List('a', 'a', 'a', 'a', 'b', 'c', 'c', 'a', 'a', 'd', 'e', 'e', 'e', 'e'))