ref: 0b1ae8fb344e5e5a26f50fa5c2f0dbb5c1318b87 dir: /lib/std/swap.myr/
pkg std = generic swap : (a : @a#, b : @a# -> void) ;; generic swap = {a : @a#, b : @a# var t t = a# a# = b# b# = t }