let nb_sol a b =
  if a = 0 then
    if b = 0 then -1
    else 0
  else 1

let g x y = 2 * x + y

let h x = g x x

let rec fact n =
  if n = 0 then 1
  else n * fact (n - 1)

let rec pow2 x =
  if x = 0 then 1
  else 2 * pow2 (x - 1)

let f x =  x + x > 4

let compose f g = fun x -> f (g x)

let compose_bis f g x = f (g x)