dec in: List*Node -> Bool;
var n1, n2: Node; l: List;
def in (n1, n2) = if eq(n1, n2) then "True" else "False";
    in (n1[]","[]l, n2) =  if eq(n1, n2) then "True" else in(l, n2);

dec merge: List*List -> List;
var n: Node;
    l1, l2: List;
def merge (n, l2) = n[]","[]l2 ;
    merge (n[]","[]l1, l2) = scat(n, ",", merge(l1, l2)) ;

/* (x-1) * (x-1) */
dec Sq_Sub1: Num -> Num;
var x: Num;
def Sq_Sub1 (x) = mul(y, y) where y = sub(x, "1");