--- a/scala/abacus.scala	Thu Feb 21 16:07:40 2013 +0000
+++ b/scala/abacus.scala	Fri Feb 22 14:31:34 2013 +0000
@@ -2,7 +2,7 @@
 
 import lib._
 
-// Abacus machines
+// Abacus instructions
 sealed abstract class AInst 
 case class Inc(n: Int) extends AInst
 case class Dec(n: Int, l: Int) extends AInst
@@ -11,10 +11,13 @@
 type AProg = List[AInst]
 type Regs = Map[Int, Int]
 
+// Abacus configurations
 case class AConfig(s: Int, regs: Regs)  
 
+// Abacus machines
 case class Abacus(p: AProg) {
 
+  //simple composition
   def ++ (that: Abacus) = Abacus(this.p ::: that.p)
 
   def shift(offset: Int, jump: Int) = Abacus(p.map(_ match {