diff -r e55c8e5da49f -r c7975ab7c52e scala/comp2.scala
--- a/scala/comp2.scala	Thu Feb 28 15:21:43 2013 +0000
+++ b/scala/comp2.scala	Fri Mar 01 02:56:08 2013 +0000
@@ -6,13 +6,60 @@
 import abacus._
 import recs._
 
-def arity(f: Rec) = f match {
-  case Z => 1
-  case S => 1
-  case Id(n, _) => n
-  case Cn(n, _, _) => n
-  case Pr(n, _, _) => n
-  case Mn(n, _) => n 
+def AbacusAdd(m: Int, n: Int, p: Int) = 
+  Abacus(Dec(m, 4), Inc(n), Inc(p), Goto(0), Dec(p, 7), Inc(m), Goto(4))
+
+def MVReg(m: Int, n: Int) = Abacus(Dec(m, 3), Inc(n), Goto(0))
+
+//move the registers ranging from i to i + n to range j to j + n
+def MVRegs(i: Int, j: Int, n: Int) : Abacus = n match { 
+  case 0 => Abacus() 
+  case n => MVRegs(i, j, n - 1) :+ MVReg(i + n - 1, j + n - 1)
+}
+
+// clears the first n registers
+def ClearRegs(n: Int) : Abacus = n match {
+  case 0 => Abacus()
+  case n => ClearRegs(n - 1) :+ Abacus(Dec(n - 1, 2), Goto(0))
+}
+
+def cn_merge_gs(x: List[(Abacus, Int, Int)], p: Int) : Abacus = x match {
+  case Nil => Abacus(Nil)
+  case (gprog, gpara, gn)::gs => gprog :+ MVReg(gpara, p) :+ cn_merge_gs(gs, p + 1)
+}
+
+// translation: 
+// second component is the arity of the recursive function, 
+// third componen is the maximum of registers used
+def compile_rec(f: Rec) : (Abacus, Int, Int) = f match {
+  case Z => (Abacus(Goto(1)), 1, 2)
+  case S => (AbacusAdd(0, 1, 2) :+ Abacus(Inc(1)), 1, 3)
+  case Id(i, j) => (AbacusAdd(j, i, i + 1), i, i + 2) 
+  case Cn(n, f, gs) => {
+    val cied_gs = gs.map(compile_rec)
+    val (fprog, fpara, fn) = compile_rec(f) 
+    val pstr = (1 + n :: fn :: (cied_gs.map(_._3))).max
+    val qstr = pstr + gs.length + 1 
+    (cn_merge_gs(cied_gs, pstr) :+ MVRegs(0, qstr, n) :+
+     MVRegs(pstr, 0, gs.length) :+ fprog :+ 
+     MVReg(fpara, pstr) :+ ClearRegs(gs.length) :+
+     MVReg(pstr, n) :+ MVRegs(qstr, 0, n), n,  qstr + n)
+  }
+  case Pr(n, f, g) => { 
+    val (fprog, fpara, fn) = compile_rec(f) 
+    val (gprog, gpara, gn) = compile_rec(g) 
+    val p = List(n + 3, fn, gn).max 
+    val e = gprog.p.length + 7 
+    (MVReg(n, p) :+ fprog :+ MVReg(n, n + 1) :+ 
+     ((Abacus(Dec(p, e)) :+ gprog :+ Abacus(Inc(n), Dec(n + 1, 3), Goto(1))) ++
+      Abacus(Dec(n + 2, 0), Inc (n + 1), Goto (gprog.p.length + 4))), n + 1, p + 1)
+  }
+  case Mn(n, f) => {
+    val (fprog, fpara, fn) = compile_rec(f)
+    val len = fprog.p.length
+    (fprog ++ Abacus(Dec(n + 1, len + 5), Dec(n + 1, len + 3), Goto(len + 1), Inc(n), Goto(0)), 
+     n, List(n + 1, fn).max)
+  }
 }
 
 }