diff -r 060f33b5661d -r 7a12053567d4 progs/compile_arr.scala
--- a/progs/compile_arr.scala	Tue Nov 27 07:53:57 2018 +0000
+++ b/progs/compile_arr.scala	Wed Nov 28 23:45:37 2018 +0000
@@ -12,12 +12,15 @@
 case class If(a: BExp, bl1: Block, bl2: Block) extends Stmt
 case class While(b: BExp, bl: Block) extends Stmt
 case class Assign(s: String, a: AExp) extends Stmt
+case class AssignA(s: String, a1: AExp, a2: AExp) extends Stmt
 case class Write(s: String) extends Stmt  // writes out a variable
+case class Array(s: String, n: Int) extends Stmt 
 
 // arithmetic expressions
 case class Var(s: String) extends AExp
 case class Num(i: Int) extends AExp
 case class Aop(o: String, a1: AExp, a2: AExp) extends AExp
+case class Ref(s: String, a1: AExp) extends AExp
 
 // boolean expressions
 case object True extends BExp
@@ -136,6 +139,24 @@
   case Write(x) => 
     (List("iload " + env(x) + "\n" + 
            "invokestatic XXX/XXX/write(I)V\n"), env)
+  case Array(s, n) => {
+    val index = if (env.isDefinedAt(s)) throw new Exception("Array already defined") else 
+                    env.keys.size.toString
+    (List("ldc " ++ n.toString ++ "\n",
+          "newarray int \n",
+          "astore " ++ index ++ "\n"), env + (s -> index))
+  } 
+  case AssignA(s, a1, a2) => {
+    val index = if (env.isDefinedAt(s)) env(s) else 
+                    throw new Exception("Array not yet defined")
+    (List("aload " + index) ++
+     compile_aexp(a1, env) ++
+     compile_aexp(a2, env) ++
+     List("iastore"), env)
+      
+      compile_aexp(a, env) ++ 
+     List("istore " + index + "\n"), env + (x -> index))
+  } 
 }
 
 // compilation of a block (i.e. list of instructions)
@@ -217,6 +238,12 @@
 
 compile_run(fib_test, "fib")
 
+val arr_test = 
+  List(Assign("x", Num(0)),
+       Array("a", 10))   
+
+compile_block(arr_test, Map())._1.mkString
+compile_run(arr_test, "arr")
 
 
 val arr_test =