-- The three statements below beginning "type" may be omitted
-- but the code is then more fragile.
data Term = Con Int | Div Term Term;
type M a = (a, Count);
type Count = Int;

answer, err :: Term;
answer = (Div (Div (Con 1972) (Con 2)) (Con 23));
err = (Div (Con 1)(Con 0));

eval :: Term -> M Int;
eval (Con a) = (a, 0);
eval (Div t u) = let {(a, ca) = eval t; 
                      (b, cb) = eval u} in (div a b, 1+ca+cb);
main = print (eval answer)

-- > (42,2)