Availability:built-in
succ(?Int1,
?Int2)True if Int2 = Int1 + 1 and Int1
>=. At least one of the arguments must be instantiated to a
natural number. This predicate raises the domain error not_less_than_zero
if called with a negative integer. E.g. succ(X, 0) fails
silently and succ(X, -1) raises a domain error.121The
behaviour to deal with natural numbers only was defined by Richard
O'Keefe to support the common count-down-to-zero in a natural way. Up to
5.1.8, succ/2
also accepted negative integers.