--- a/progs/lecture1.scala	Sat Nov 09 22:04:53 2019 +0000
+++ b/progs/lecture1.scala	Mon Nov 11 13:24:12 2019 +0000
@@ -460,62 +460,6 @@
 
 test()
 
-// Option type
-//=============
-
-//in Java if something unusually happens, you return null or something
-//
-//in Scala you use Options instead
-//   - if the value is present, you use Some(value)
-//   - if no value is present, you use None
-
-
-List(7,2,3,4,5,6).find(_ < 4)
-List(5,6,7,8,9).find(_ < 4)
-
-
-
-// error handling with Options (no exceptions)
-//
-//  Try(something).getOrElse(what_to_do_in_case_of_an_exception)
-//
-import scala.util._
-import io.Source
-
-val my_url = "https://nms.kcl.ac.uk/christian.urban/"
-
-Source.fromURL(my_url).mkString
-
-Try(Source.fromURL(my_url).mkString).getOrElse("")
-
-Try(Some(Source.fromURL(my_url).mkString)).getOrElse(None)
-
-
-// the same for files
-Try(Some(Source.fromFile("text.txt").mkString)).getOrElse(None)
-
-
-
-// how to implement a function for reading something from files...
-
-def get_contents(name: String) : List[String] = 
-  Source.fromFile(name).getLines.toList
-
-get_contents("test.txt")
-
-// slightly better - return Nil
-def get_contents(name: String) : List[String] = 
-  Try(Source.fromFile(name).getLines.toList).getOrElse(List())
-
-get_contents("text.txt")
-
-// much better - you record in the type that things can go wrong 
-def get_contents(name: String) : Option[List[String]] = 
-  Try(Some(Source.fromFile(name).getLines.toList)).getOrElse(None)
-
-get_contents("text.txt")
-get_contents("test.txt")
-