diff -r b4f5714485e1 -r 30943d5491b6 progs/fun.scala
--- a/progs/fun.scala	Wed Oct 02 02:09:48 2019 +0100
+++ b/progs/fun.scala	Wed Oct 02 14:05:36 2019 +0100
@@ -1,10 +1,26 @@
 // A Small Compiler for a Simple Functional Language
 // (includes an external lexer and parser)
+//
+// call with 
+//
+//     scala fun.scala fact
+//
+//     scala fun.scala defs
+//
+// this will generate a .j file and run the jasmin
+// assembler (installed at jvm/jasmin-2.4/jasmin.jar)
+// it runs the resulting JVM file twice for timing 
+// purposes.
 
-import java.io._
+
+
 
 object Compiler {
 
+import java.io._  
+import scala.util._
+import scala.sys.process._
+
 // Abstract syntax trees for the Fun language
 abstract class Exp extends Serializable 
 abstract class BExp extends Serializable 
@@ -165,16 +181,15 @@
   (end - start)/(i * 1.0e9)
 }
 
-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 compile(class_name: String) : String = {
-  val ast = deserialise[List[Decl]](class_name ++ ".prs") 
+  val ast = deserialise[List[Decl]](class_name ++ ".prs").getOrElse(Nil) 
   val instructions = ast.map(compile_decl).mkString
   (library + instructions).replaceAllLiterally("XXX", class_name)
 }
@@ -184,9 +199,7 @@
   scala.tools.nsc.io.File(s"${class_name}.j").writeAll(output)
 }
 
-import scala.sys.process._
-
-def compile_run(class_name: String) : Unit = {
+def compile_and_run(class_name: String) : Unit = {
   compile_to_file(class_name)
   (s"java -jar jvm/jasmin-2.4/jasmin.jar ${class_name}.j").!!
   println("Time: " + time_needed(2, (s"java ${class_name}/${class_name}").!))
@@ -194,12 +207,13 @@
 
 
 // some examples of .fun files
-//compile_file("fact")
-//compile_run("defs")
-//compile_run("fact")
+//compile_to_file("fact")
+//compile_and_run("fact")
+//compile_and_run("defs")
+
 
 def main(args: Array[String]) = 
-   compile_run(args(0))
+   compile_and_run(args(0))
 
 
 }
\ No newline at end of file