diff -r 4980f421b3b0 -r c112a6cb5e52 progs/compile_arr.scala
--- a/progs/compile_arr.scala	Mon Jan 27 10:11:44 2020 +0000
+++ b/progs/compile_arr.scala	Tue Jan 28 12:23:53 2020 +0000
@@ -101,34 +101,49 @@
   case "*" => i"imul"
 }
 
+def compile_num(i: Int) = 
+  if (0 <= i && i <= 5) i"iconst_$i" else i"ldc $i"
+
+def compile_aload(i: Int) = 
+  if (0 <= i && i <= 3) i"aload_$i" else i"aload $i"
+
+def compile_iload(i: Int) = 
+  if (0 <= i && i <= 3) i"iload_$i" else i"iload $i"
+
+def compile_istore(i: Int) = 
+  if (0 <= i && i <= 3) i"istore_$i" else i"istore $i"
+
 // arithmetic expression compilation
 def compile_aexp(a: AExp, env : Env) : String = a match {
-  case Num(i) => i"ldc $i"
-  case Var(s) => i"iload ${env(s)}"
+  case Num(i) => compile_num(i)
+  case Var(s) => compile_iload(env(s))
   case Aop(op, a1, a2) => 
     compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ compile_op(op)
-  case Ref(s, a) =>
-    i"aload ${env(s)}" ++ compile_aexp(a, env) ++  i"iaload"
+  case Ref(s, a) => 
+    compile_aload(env(s)) ++ compile_aexp(a, env) ++  i"iaload"
 }
 
+def compile_bop(op: String, jmp: String) = op match {
+  case "==" => i"if_icmpne $jmp"
+  case "!=" => i"if_icmpeq $jmp"
+  case "<"  => i"if_icmpge $jmp"
+}
+
+
 // boolean expression compilation
 def compile_bexp(b: BExp, env : Env, jmp: String) : String = b match {
   case True => ""
   case False => i"goto $jmp"
-  case Bop("==", a1, a2) => 
-    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ i"if_icmpne $jmp"
-  case Bop("!=", a1, a2) => 
-    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ i"if_icmpeq $jmp"
-  case Bop("<", a1, a2) => 
-    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ i"if_icmpge $jmp"
+  case Bop(op, a1, a2) => 
+    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ compile_bop(op, jmp)
 }
 
 // statement compilation
 def compile_stmt(s: Stmt, env: Env) : (String, Env) = s match {
   case Skip => ("", env)
   case Assign(x, a) => {
-     val index = env.getOrElse(x, env.keys.size)
-    (compile_aexp(a, env) ++ i"istore $index \t\t; $x", env + (x -> index)) 
+     val index = env.getOrElse(x, env.keys.size) //
+    (compile_aexp(a, env) ++ compile_istore(index), env + (x -> index)) 
   } 
   case If(b, bl1, bl2) => {
     val if_else = Fresh("If_else")
@@ -153,12 +168,12 @@
      l"$loop_end", env1)
   }
   case Write(x) => 
-    (i"iload ${env(x)} \t\t; $x" ++ 
+    (compile_iload(env(x)) ++
      i"invokestatic XXX/XXX/write(I)V", env)
   case Read(x) => {
     val index = env.getOrElse(x, env.keys.size) 
-    (i"invokestatic XXX/XXX/read()I" ++ 
-     i"istore $index \t\t; $x", env + (x -> index))
+    (i"invokestatic XXX/XXX/read()I" ++     
+     compile_istore(index), env + (x -> index))
   }
   case ArrayDef(s: String, n: Int) => {
     val index = if (env.isDefinedAt(s)) throw new Exception("array def error") else 
@@ -170,7 +185,7 @@
   case AssignA(s, a1, a2) => {
     val index = if (env.isDefinedAt(s)) env(s) else 
                     throw new Exception("array not defined")
-    (i"aload ${env(s)}" ++
+    (compile_aload(env(s)) ++
      compile_aexp(a1, env) ++
      compile_aexp(a2, env) ++
      i"iastore", env)
@@ -243,7 +258,7 @@
   println("generated .j file")
   (s"java -jar jvm/jasmin-2.4/jasmin.jar ${class_name}.j").!!
   println("generated .class file ")
-  println("Time: " + time_needed(1, (s"java ${class_name}/${class_name}").!)._1)
+  println("Time: " + time_needed(3, (s"java ${class_name}/${class_name}").!)._1)
 }
 
 
@@ -510,8 +525,9 @@
 // Mandelbrot Set
 //----------------
 //
-// Note: Parsing of the generated WHILE program (around 60K in size)
-// takes approximately 10 minutes
+// Note: Parsing of the generated WHILE program (around 56K in size)
+// takes approximately 10 minutes. The final class file runs
+// for around 23 seconds.
 
 bf_run("""A mandelbrot set fractal viewer in brainf*** written by Erik Bosman
 +++++++++++++[->++>>>+++++>++>+<<<<<<]>>>>>++++++>--->>>>>>>>>>+++++++++++++++[[