--- a/progs/lecture1.scala	Mon Nov 06 21:49:55 2023 +0000
+++ b/progs/lecture1.scala	Fri Dec 08 00:54:36 2023 +0000
@@ -1,7 +1,7 @@
 // Scala Lecture 1
 //=================
 
-// - List, Sets, Strings, ... 
+// - List, Sets, Ints, Strings, ... 
 // - Value assignments (val vs var)
 // - How to define functions? (What is returned?)
 // - If-Conditions
@@ -19,31 +19,14 @@
 val x = 42
 val y = 3 + 4 
 val z = x / y
-val x = 70
+val x = 0
 println(z)
 
 
 // (you cannot reassign values: z = 9 will give an error)
-//var z = 9
-//z = 10
-
-
-// Hello World
-//=============
-
-// an example of a stand-alone Scala file
-// (in the assignments you must submit a plain Scala script)
+var z = 9
+z = 10
 
-object Hello extends App { 
-  println("hello world")
-}
-
-// can then be called with
-//
-// $> scalac hello-world.scala
-// $> scala Hello
-//
-// $> java -cp /usr/local/src/scala/lib/scala-library.jar:. Hello
 
 
 
@@ -56,6 +39,7 @@
 // picking an element in a list
 val lst = List(1, 2, 3, 1)
 
+
 lst(0)
 lst(2)
 
@@ -84,7 +68,7 @@
 
 // Equality in Scala is structural
 //=================================
-val a = "Dave"
+val a = "Dave2"
 val b = "Dave"
 
 if (a == b) println("Equal") else println("Unequal")
@@ -159,7 +143,6 @@
 "1,2,3,4,5".split(",").toList
 "1,2,3,4,5".split(",3,").mkString("\n")
 
-"abcdefg".startsWith("abc")
 
 
 // Types (see slide)
@@ -241,6 +224,36 @@
 //  }
 
 
+// > LENGTH OF LIST EXAMPLE
+def len(xs: List[Int], acc: Int) : Int = {
+   if (xs == Nil) acc
+   else foo(xs.tail, acc + 1)
+}
+
+def len(xs: List[Int]) : Int = foo(xs, 0)
+
+len(List(1,2,3,4,1))
+
+
+def len(xs: List[Int]) : Int = {
+    if (xs == Nil) 0
+    else (1 + len(xs.tail))
+}    
+
+
+
+len(List(1,2,3,4,1))
+
+
+
+def len(xs: List[Int]) : Int = xs match {
+   case Nil => 0
+   case x :: xs => 1 + len(xs)
+}
+
+len(List(1,2,3,4,1))
+
+
 
 // If-Conditionals
 //=================
@@ -318,7 +331,7 @@
 }
 
 for (n <- (1 to 10).toList; 
-     m <- (1 to 5).toList) yield (n, m, n * m)
+     m <- (1 to 5).toList) yield (n, m)
 
 
 // you can assign the result of a for-comprehension
@@ -327,8 +340,11 @@
   for (n <- (1 to 10).toList; 
        m <- (1 to 10).toList) yield n * m
 
-println(mult_table.mkString)
-mult_table.sliding(10,10).mkString("\n")
+println(mult_table.mkString(","))
+mult_table.sliding(10,10).toList
+
+
+.mkString("\n")
 
 // for-comprehensions also work for other
 // collections
@@ -336,11 +352,17 @@
 for (n <- Set(10,12,4,5,7,8,10)) yield n * n
 
 for (n <- (1 to 10)) yield {
+
   n * n  
 }
 
 // with if-predicates / filters
 
+val xs = for (n <- (1 to 3).toList; 
+     m <- (1 to 3).toList) yield (n,m)
+
+xs.filter{case (m, n) => (n + m) % 2 == 0}    
+
 for (n <- (1 to 3).toList; 
      m <- (1 to 3).toList;
      if (n + m) % 2 == 0) yield (n, m)
@@ -350,7 +372,7 @@
 
 val lst = List((1, 4), (2, 3), (3, 2), (4, 1))
 
-for ((m, n) <- lst) yield m + n 
+` yield m + n 
 
 for (p <- lst) yield p._1 + p._2 
 
@@ -369,9 +391,11 @@
 // with only a side-effect (no list is produced),
 // has no "yield"
 
-for (n <- (1 to 10).toList) println(n * n)
+val xs = for (n <- (1 to 10).toList) yield println(n * n)
 
-for (n <- (1 to 10).toList) yield n * n
+xs.tail
+
+val foo = for (n <- (1 to 10).toList) yield n * n
 
 
 // BTW: a roundabout way of printing out a list, say
@@ -450,15 +474,21 @@
 // - no mutable data-structures (no Arrays, no ListBuffers)
 
 // But what the heck....lets try to count to 1 Mio in parallel
+// 
+// requires
+// scala-cli --extra-jars scala- parallel-collections_3-1.0.4.jar
+
 import scala.collection.parallel.CollectionConverters._
 
-var cnt = 0
+def test() = {
+  var cnt = 0
 
-for(i <- (1 to 100_000).par) cnt += 1
+  for(i <- (1 to 100_000)) cnt += 1
 
-println(s"Should be 100000: $cnt")
+  println(s"Should be 100000: $cnt")
+}
 
-
+test()
 
 // Or
 // Q: Count how many elements are in the intersections of