ref: ce93c2af0b4aeb2c40a05f2b45c1397b7a2ced23 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 }