tasks a-s

Task/Parametric-polymorphism/Scala/parametric-polymorphism-1.scala

@@ -0,0 +1,4 @@
+case class Tree[+A](value: A, left: Option[Tree[A]], right: Option[Tree[A]]) {
+  def map[B](f: A => B): Tree[B] =
+    Tree(f(value), left map (_.map(f)), right map (_.map(f)))
+}

Task/Parametric-polymorphism/Scala/parametric-polymorphism-2.scala

@@ -0,0 +1,5 @@
+class Employee(val name: String)
+class Manager(name: String) extends Employee(name)
+
+val t = Tree(new Manager("PHB"), None, None)
+val t2: Tree[Employee] = t

Task/Parametric-polymorphism/Scala/parametric-polymorphism-3.scala

@@ -0,0 +1,2 @@
+def toName(e: Employee) = e.name
+val treeOfNames = t.map(toName)

Task/Parametric-polymorphism/Scala/parametric-polymorphism-4.scala

@@ -0,0 +1 @@
+trait Function1[-T1, +R]

Task/Parametric-polymorphism/Scala/parametric-polymorphism-5.scala

@@ -0,0 +1,6 @@
+case class Tree[+A](value: A, left: Option[Tree[A]], right: Option[Tree[A]]) {
+  def map[B](f: A => B): Tree[B] =
+    Tree(f(value), left map (_.map(f)), right map (_.map(f)))
+  def find[B >: A](what: B): Boolean =
+    (value == what) || left.map(_.find(what)).getOrElse(false) || right.map(_.find(what)).getOrElse(false)
+}

Task/Parametric-polymorphism/Scala/parametric-polymorphism-6.scala

@@ -0,0 +1,2 @@
+if (t2.find(new Employee("Dilbert")))
+  println("Call Catbert!")

Task/Parametric-polymorphism/Scala/parametric-polymorphism-7.scala

@@ -0,0 +1,4 @@
+trait DFA {
+  type Element
+  val map = new collection.mutable.HashMap[Element, DFA]()
+}