#def negation: cu%?%d%:_
#def negation: c=
#def signum: i$$*c$ul_^^$*-%u%:_d/o
#def less than: -$$*c$ul_^^$*-%u%:_d/cd=
#def magic: ic%?%cuuuuu:$*%cuu/@+%:
ilcuu/ruR:rldRor:
#def stack_not_empty: ?d:u
#def magic: ilcuu/%u%:ldo: