negate : NTP ;
-- This routine returns the negation of self provided that this is
-- representable in the value domain. Note that this is an implementation
-- issue dependent upon the numeric model designed into the CPU -- eg if
-- it is twos-complement then it is not possible to negate the minimum
-- value.
negatable : BOOL ;
-- This routine returns true if and only if the negated value of
-- self is within the value domain of the class NTP.
is_neg : BOOL ;
-- This feature returns true if and only if the number is negative.