diff -r 86a456f8cb92 -r 135bf034ac30 progs/lecture2.scala
--- a/progs/lecture2.scala	Sat Sep 23 23:49:44 2023 +0100
+++ b/progs/lecture2.scala	Wed Nov 01 15:01:32 2023 +0000
@@ -1,54 +1,11 @@
 // Scala Lecture 2
 //=================
  
-
-// String Interpolations
-//=======================
-
-def cube(n: Int) : Int = n * n * n
-
-val n = 3
-println("The cube of " + n + " is " + cube(n) + ".")
-
-println(s"The cube of $n is ${cube(n)}.")
-
-// or even
-
-println(s"The cube of $n is ${n * n * n}.")
-
-// helpful for debugging purposes
-//
-//     "The most effective debugging tool is still careful 
-//          thought, coupled with judiciously placed print 
-//                                             statements."
-//       — Brian W. Kernighan, in Unix for Beginners (1979)
-
-
-def gcd_db(a: Int, b: Int) : Int = {
-  println(s"Function called with $a and $b.")
-  if (b == 0) a else gcd_db(b, a % b)
-}
-
-gcd_db(48, 18)
-
-
-
-// you can also implement your own string interpolations
-
-import scala.language.implicitConversions
-import scala.language.reflectiveCalls
-
-implicit def sring_inters(sc: StringContext) = new {
-    def i(args: Any*): String = s"\t${sc.s(args:_*)}\n"
-    def l(args: Any*): String = s"${sc.s(args:_*)}:\n"
-}
-
-// this allows you to write things like
-
-i"add ${3+2}" 
-l"some_fresh_name"
-
-
+// - Options
+// - Higher-Order Functions (short-hand notation)
+// - maps (behind for-comprehensions)
+// - Pattern-Matching
+// - Recursion
 
 // The Option Type
 //=================
@@ -79,6 +36,7 @@
 safe_div(10 + 5, 4 - 1)  
 
 List(1,2,3,4,5,6).indexOf(7)
+List[Int]().min
 List[Int]().minOption
 
 def my_min(ls: List[Int]) : Option[Int] = 
@@ -92,8 +50,8 @@
 //  Try(something).getOrElse(what_to_do_in_case_of_an_exception)
 //
 
-import scala.util._
-import io.Source
+import scala.util._      // Try,...
+import io.Source         // fromURL
 
 val my_url = "https://nms.kcl.ac.uk/christian.urban/"
 
@@ -399,9 +357,10 @@
 // Pattern Matching
 //==================
 
-// A powerful tool which is supposed to come to Java in 
-// a few years time (https://www.youtube.com/watch?v=oGll155-vuQ).
-// ...Scala already has it for many years ;o)
+// A powerful tool which has even landed in Java during 
+// the last few years (https://inside.java/2021/06/13/podcast-017/).
+// ...Scala already has it for many years and the concept is
+// older than your friendly lecturer, that is stone old  ;o)
 
 // The general schema:
 //
@@ -420,8 +379,8 @@
     case x::xs => f(x)::my_map_int(xs, f)
   }
 
-def my_map_option(o: Option[Int], f: Int => Int) : Option[Int] = 
-  o match {
+def my_map_option(opt: Option[Int], f: Int => Int) : Option[Int] = 
+  opt match {
     case None => None
     case Some(x) => Some(f(x))
   }