--- a/progs/fun_parser.scala	Wed Oct 02 02:09:48 2019 +0100
+++ b/progs/fun_parser.scala	Wed Oct 02 14:05:36 2019 +0100
@@ -1,10 +1,20 @@
-// A Small Compiler for a Simple Functional Language
-// (includes a lexer and a parser)
+// A parser for the Fun language
+//================================
+//
+// call with 
+//
+//     scala fun_parser.scala fact.tks
+//
+//     scala fun_parser.scala defs.tks
+//
+// this will generate a .prs file that can be deserialised back
+// into a list of declarations
 
 object Fun_Parser {
 
 import scala.language.implicitConversions    
 import scala.language.reflectiveCalls
+import scala.util._ 
 import java.io._
 
 abstract class Token extends Serializable 
@@ -162,28 +172,29 @@
 // Reading tokens and Writing parse trees
 
 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 deserialise[T](fname: String) : T = {
-  val in = new ObjectInputStream(new FileInputStream(fname))
-  val data = in.readObject.asInstanceOf[T]
-  in.close
-  data
+def deserialise[T](fname: String) : Try[T] = {
+  import scala.util.Using
+  Using(new ObjectInputStream(new FileInputStream(fname))) {
+    in => in.readObject.asInstanceOf[T]
+  }
 }
 
 
-def main(args: Array[String]) = {
+def main(args: Array[String]) : Unit= {
   val fname = args(0)
   val pname = fname.stripSuffix(".tks") ++ ".prs"
-  val tks = deserialise[List[Token]](fname)
+  val tks = deserialise[List[Token]](fname).getOrElse(Nil)
   serialise(pname, Prog.parse_single(tks))
 
   // testing whether read-back is working
-  //val ptree = deserialise[List[Decl]](pname)
+  //val ptree = deserialise[List[Decl]](pname).get
   //println(s"Reading back from ${pname}:\n${ptree.mkString("\n")}")  
 }
 
-}
\ No newline at end of file
+}