diff -r 80c691a4caab -r 7a0735db4788 wsheets/wsh01.scala
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wsheets/wsh01.scala	Mon Nov 14 12:04:21 2022 +0000
@@ -0,0 +1,109 @@
+
+// Task 1
+
+2 + 2
+1 / 2
+1.0 / 2
+1 / 2.0
+1 / 0
+1.0 / 0.0
+true == false
+true && false
+1 > 1.0
+"12345".length
+List(1,2,1).size
+Set(1,2,1).size
+List(1) == List(1)
+Set(1,2,3) == Set(3,2,1)
+Array(1) == Array(1)
+Array(1).sameElements(Array(1))
+
+
+// Task 2
+
+val z = 42
+z = z + 1 .       // error
+val x = 2 * z
+val z = 466       // old z not accessible anymore
+println(x)
+
+
+// Task 3
+println("Hello " ++ "World")
+List(1,2,3,4).mkString("\n")
+List(1,2,3,4).mkString("(", "|", ")")
+
+
+// Task 4
+def miles2meters(m: Int): Int = m * 1609
+
+
+// Task 5
+
+val s1 = "foo"
+val s2 = "bar"
+val s3 = "foobar"
+if (s1 == s2) print("equal") else print("unequal")
+if (s1 ++ s2 == s3) print("equal") else print("unequal")
+
+
+// Task 6
+for (x <- (1 to 5).toList;
+     y <- (1 to 5).toList;
+     z <- (1 to 5).toList) yield (x,y,z)
+
+for (x <- (1 to 5).toList;
+     y <- (1 to 5).toList;
+     z <- (1 to 5).toList;
+     if (x + y + z) % 3 == 0) yield (x,y,z)
+
+(for (x <- (1 to 5).toList;
+     y <- (1 to 5).toList;
+     z <- (1 to 5).toList;
+     if (x + y + z) % 3 == 0) yield (x,y,z)).sortBy(_._2)
+
+
+
+// Task 7
+
+// first version with using an accumulator
+
+def cnt(xs: List[Int], acc: List[(Int, Int)] = Nil) : List[(Int, Int)] = 
+  (xs, acc) match { 
+    case (Nil, acc) => acc.reverse
+    case (x::xs, Nil) => cnt(xs, (x, 1)::Nil)
+    case (x::xs, (y, n)::ys) =>  
+        if (x == y) cnt(xs, (y, n + 1)::ys)
+        else cnt(xs, (x, 1)::(y, n)::ys)
+  }
+
+def toStr(p: (Int, Int)) = 
+    if (p._2 == 1) s"${p._1}" else s"${p._2} x ${p._1}"
+
+def pp_list(xs: List[Int]) = {
+   cnt(xs).map(toStr) 
+}
+
+pp_list(List(1,1,1,2,3,3))    //   List(3 x 1, 2, 2 x 3)
+pp_list(List(1,2,3,4,4,4))    //   List(1, 2, 3, 3 x 4)
+pp_list(List(1,1,1,1,1,1))    //   List(6 x 1)
+pp_list(List(1,1,1,2,1,1))    //   List(3 x 1, 2, 2 x 1)
+
+// second version with just a simple counter
+
+def cnt2(xs: List[Int], n : Int = 0) : List[(Int, Int)] = xs match {
+  case Nil => Nil
+  case x::Nil => (x, n + 1)::Nil
+  case x::y::tail => 
+    if (x == y) cnt2(y::tail, n + 1) 
+    else (x, n + 1)::cnt2(y::tail, 0)   
+}
+
+def pp_list2(xs: List[Int]) = {
+   cnt2(xs).map(toStr) 
+}
+
+pp_list2(List(1,1,1,2,3,3))    //   List(3 x 1, 2, 2 x 3)
+pp_list2(List(1,2,3,4,4,4))    //   List(1, 2, 3, 3 x 4)
+pp_list2(List(1,1,1,1,1,1))    //   List(6 x 1)
+pp_list2(List(1,1,1,2,1,1))    //   List(3 x 1, 2, 2 x 1)
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