Ленивость в окамле

utop[0]> open Core.Std;;
utop[1]> let a = lazy (printf "A\n"; 0);;
val a : int lazy_t = <lazy>
utop[2]> let b (a : int) = lazy (printf "B\n"; 0);;
val b : int -> int lazy_t = <fun>
utop[3]> Lazy.force Lazy.(a >>= b);;
A
B
- : int = 0

Ну ё-моё...