--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/fun/simple-cps.sc	Tue May 30 13:27:54 2023 +0100
@@ -0,0 +1,63 @@
+// Source language: arithmetic expressions with function calls 
+enum Expr {
+    case Num(n: Int)
+    case Aop(op: String, e1: Expr, e2: Expr)
+    case Call(fname: String, args: List[Expr])
+}
+import Expr._
+
+// Target language 
+// "trivial" KValues
+enum KVal {
+    case KVar(s: String)
+    case KNum(n: Int)
+    case KAop(op: String, v1: KVal, v2: KVal)
+    case KCall(fname: String, args: List[KVal])
+}
+import KVal._
+
+// KExpressions 
+enum KExp {
+    case KReturn(v: KVal)
+    case KLet(x: String, v: KVal, e: KExp)
+}
+import KExp._
+
+var cnt = -1
+def Fresh(s: String) = {
+    cnt = cnt + 1
+    s"${s}_${cnt}"
+}
+
+def CPS(e: Expr)(k: KVal => KExp): KExp = e match { 
+    case Num(i) => k(KNum(i))
+    case Aop(op, l, r) => {
+        val z = Fresh("z")
+        CPS(l)(l => 
+          CPS(r)(r => KLet(z, KAop(op, l, r), k(KVar(z)))))
+    }
+    case Call(fname, args) => {
+        def aux(args: List[Expr], vs: List[KVal]) : KExp = args match {
+            case Nil => {
+                val z = Fresh("tmp")
+                KLet(z, KCall(fname, vs), k(KVar(z)))
+            }
+            case a::as => CPS(a)(r => aux(as, vs ::: List(r)))
+        }
+        aux(args, Nil)  
+    }
+}
+
+def CPSi(e: Expr) : KExp = CPS(e)(KReturn(_))
+
+
+//1 + foo(bar(4 * -7), 3, id(12))
+val etest = 
+    Aop("+", Num(1),
+             Call("foo", 
+                List(Call("bar", 
+                             List(Aop("*", Num(4), Num(-7)))), 
+                     Num(3), 
+                     Call("id", List(Num(12))))))
+
+println(CPSi(etest))