F partial(f, g)
   F fg(x)
      R @f(@g, x)
   R fg

F main()
   F ffs(f, x)
      R x.map(a -> @f(a))
   F f1(a) {R a * 2}
   F f2(a) {R a * a}

   V fsf1 = partial(ffs, f1)
   V fsf2 = partial(ffs, f2)

   print(fsf1([1, 2, 3, 4]))
   print(fsf2([1, 2, 3, 4]))

main()