diff -r 018b9c12ee1f -r f7bcb27d1940 progs/lecture1.scala
--- a/progs/lecture1.scala	Fri Nov 09 07:30:02 2018 +0000
+++ b/progs/lecture1.scala	Thu Nov 15 03:35:38 2018 +0000
@@ -5,11 +5,11 @@
 // (their names should be lower case)
 //====================================
 
+
 val x = 42
 val y = 3 + 4
 val z = x / y
 
-
 // (you cannot reassign values: z = 9 will give an error)
 
 
@@ -57,11 +57,15 @@
 val a = "Dave"
 val b = "Dave"
 
-if (a == b) println("equal") else println("unequal")
+if (a == b) println("Equal") else println("Unequal")
 
 Set(1,2,3) == Set(3,1,2)
 List(1,2,3) == List(3,1,2)
 
+val n1 = 3 + 7
+val n2 = 5 + 5
+
+n1 == n2
 
 // this applies to "concrete" values;
 // you cannot compare functions
@@ -77,13 +81,14 @@
 
 val lst = List(1,2,3,1)
 
+
 println(lst.toString)
-println(lst.mkString("\n"))
+println(lst.mkString(","))
 
 println(lst.mkString(", "))
 
 // some methods take more than one argument
-println(lst.mkString("[", ",", "]"))
+println(lst.mkString("{", ",", "}"))
 
 
 
@@ -92,7 +97,7 @@
 
 List(1,2,3,1).toString
 List(1,2,3,1).toSet
-"hello".toList
+"hello".toList.tail
 1.toDouble
 
 
@@ -108,6 +113,7 @@
 List(1,2,3,4,3).indexOf(3)
 
 "1,2,3,4,5".split(",").mkString("\n")
+"1,2,3,4,5".split(",").toList
 "1,2,3,4,5".split(",3,").mkString("\n")
 
 "abcdefg".startsWith("abc")
@@ -155,6 +161,7 @@
 def double(x: Int) : Int = x + x
 def square(x: Int) : Int = x * x
 
+def str(x: Int) : String = x.toString
 square(6)
 
 
@@ -172,8 +179,8 @@
 //
 
 def silly(n: Int) : Int = {
-  n * n
-  n + n
+  if (n < 10) n * n
+  else n + n
 }
 
 
@@ -211,8 +218,13 @@
 
 //gcd - Euclid's algorithm
 
-def gcd(a: Int, b: Int) : Int =
-  if (b == 0) a else gcd(b, a % b)
+def gcd(a: Int, b: Int) : Int = {
+  if (b == 0) a 
+  else {
+    val foo = 42
+    gcd(b, a % b)
+  }  
+}
 
 gcd(48, 18)
 
@@ -245,7 +257,7 @@
 import scala.util._
 import io.Source
 
-val my_url = "https://nms.kcl.ac.uk/christian.urban/"
+val my_url = "https://nms.imperial.ac.uk/christian.urban/"
 
 Source.fromURL(my_url).mkString
 
@@ -255,7 +267,7 @@
 
 
 // the same for files
-Source.fromFile("test.txt").mkString
+Try(Some(Source.fromFile("text.txt").mkString)).getOrElse(None)
 
 // function reading something from files...
 
@@ -266,7 +278,7 @@
 
 // slightly better - return Nil
 def get_contents(name: String) : List[String] = 
-  Try(Source.fromFile(name).getLines.toList).getOrElse(Nil)
+  Try(Source.fromFile(name).getLines.toList).getOrElse(List())
 
 get_contents("text.txt")
 
@@ -313,7 +325,10 @@
 // For-Comprehensions (not For-Loops)
 //====================================
 
-for (n <- (1 to 10).toList) yield square(n)
+
+for (n <- (1 to 10).toList) yield { 
+  square(n) + 1
+}
 
 for (n <- (1 to 10).toList; 
      m <- (1 to 10).toList) yield m * n
@@ -323,22 +338,24 @@
   for (n <- (1 to 10).toList; 
        m <- (1 to 10).toList) yield m * n
 
+println(mult_table.mkString)
 mult_table.sliding(10,10).mkString("\n")
 
 // the list/set/... can also be constructed in any 
 // other way
-for (n <- List(10,12,4,5,7,8,10)) yield n * n
+for (n <- Set(10,12,4,5,7,8,10)) yield n * n
 
 
 // with if-predicates / filters
 
 for (n <- (1 to 3).toList; 
      m <- (1 to 3).toList;
-     if (n + m) % 2 == 0) yield (n, m)
+     if (n + m) % 2 == 0;
+     if (n * m) < 2) yield (n, m)
 
 for (n <- (1 to 3).toList; 
      m <- (1 to 3).toList;
-     if ((n + m) % 2 == 0)) yield (n, m)
+     if ((((n + m) % 2 == 0)))) yield (n, m)
 
 // with patterns
 
@@ -389,6 +406,8 @@
 // BTW: a roundabout way of printing out a list, say
 val lst = ('a' to 'm').toList
 
+for (n <- lst) println(n)
+
 for (i <- (0 until lst.length)) println(lst(i))
 
 // Why not just? Why making your life so complicated?