const n:int = 100

type st = On | Off

node f(a:int^n at r; c:st) returns (o:int^n at r)
var u,v,x:int^n at r;
let
  (u, v) = split c (a);
  x = [ u with [0] = 0 ];
  o = merge c (On -> x) (Off -> v)
tel