succ : NTP ;
-- This feature returns the ordinal number which is next in sequence
-- after self.
succ(
count : NTP
) : NTP ;
-- This feature returns the ordinal number which is offset towards a
-- higher number by count from self!
pred : NTP ;
-- This feature returns the ordinal number which precedes self in
-- sequence.
pred(
count : NTP
) : NTP ;
-- This feature returns the ordinal number which is offset towards a
-- lower number by count from self!