--- a/scala/abacus.scala	Fri Feb 22 14:31:34 2013 +0000
+++ b/scala/abacus.scala	Mon Feb 25 15:12:48 2013 +0000
@@ -18,7 +18,9 @@
 case class Abacus(p: AProg) {
 
   //simple composition
-  def ++ (that: Abacus) = Abacus(this.p ::: that.p)
+  def ++ (that: Abacus) = Abacus(p ::: that.p)
+
+  def :+ (that: Abacus) = this ++ that.shift(p.length, -1)
 
   def shift(offset: Int, jump: Int) = Abacus(p.map(_ match {
     case Inc(n) => Inc(n)
@@ -56,5 +58,11 @@
   def run(regs: Regs): Regs = run(AConfig(0, regs)).regs
 }
 
+// some syntactical convenience
+object Abacus {
+  def apply(is: AInst*) : Abacus = Abacus(is.toList)
 }
 
+
+}
+