diff -r b4f5714485e1 -r 30943d5491b6 progs/tokenise.scala
--- a/progs/tokenise.scala	Wed Oct 02 02:09:48 2019 +0100
+++ b/progs/tokenise.scala	Wed Oct 02 14:05:36 2019 +0100
@@ -6,6 +6,11 @@
 //     scala tokenise.scala fib.while
 //
 //     scala tokenise.scala loops.while
+//
+// this will generate a .tks file that can be deserialised back
+// into a list of tokens
+// you can add -Xno-patmat-analysis in order to get rid of the
+// match-not-exhaustive warning
 
 object Tokenise {
 
@@ -188,8 +193,10 @@
   env(lex_simp(r, s.toList))
 
 
-// The Lexing Rules for the Fun Language
+// The Lexing Rules for the WHILE Language
 
+// inefficient representations for some extended regular
+// expressions
 def PLUS(r: Rexp) = r ~ r.%
 
 def Range(s : List[Char]) : Rexp = s match {
@@ -223,8 +230,8 @@
 
 
 
-// Generating tokens for the WHILE language
-// and serialising them into a .tks file
+// Generate tokens for the WHILE language
+// and serialise them into a .tks file
 
 import java.io._
 
@@ -238,6 +245,7 @@
 case class T_KWD(s: String) extends Token
 case class T_STR(s: String) extends Token
 
+// transforms pairs into tokens
 val token : PartialFunction[(String, String), Token] = {
   case ("s", _) => T_SEMI
   case ("p", "{") => T_LPAREN
@@ -249,21 +257,23 @@
   case ("str", s) => T_STR(s)
 }
 
+// filters out all un-interesting token
 def tokenise(s: String) : List[Token] = 
   lexing_simp(WHILE_REGS, s).collect(token)
 
 
 def serialise[T](fname: String, data: T) = {
-  val out = new ObjectOutputStream(new FileOutputStream(fname))
-  out.writeObject(data)
-  out.close
+  import scala.util.Using
+  Using(new ObjectOutputStream(new FileOutputStream(fname))) {
+    out => out.writeObject(data)
+  }
 }
 
-def main(args: Array[String]) = {
+def main(args: Array[String]) : Unit = {
   val fname = args(0)
+  val tname = fname.stripSuffix(".while") ++ ".tks"
   val file = io.Source.fromFile(fname).mkString
-  val tks = fname.stripSuffix(".while") ++ ".tks"
-  serialise(tks, tokenise(file))
+  serialise(tname, tokenise(file))
 }