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|Special purpose integer arithmetic|
The predicates in this section provide more logical operations between integers. They are not covered by the ISO standard, although they are `part of the community' and found as either library or built-in in many other Prolog systems.
infinite, but some other Prolog systems already use
inffor infinity; we accept both for the time being. between/3 is true iff Value >=Low, a feature that is particularly interesting for generating integers from a certain value.
not_less_than_zeroif called with a negative integer. E.g.
succ(X, 0)fails silently and
succ(X, -1)raises a domain error.111The 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.
divmod(Dividend, Divisor, Quotient, Remainder) :- Quotient is Dividend div Divisor, Remainder is Dividend mod Divisor.
Note that this predicate is only available if SWI-Prolog is compiled with unbounded integer support. This is the case for all packaged versions.
% I < 0, % N mod 2 =\= 0, nth_integer_root_and_remainder( N, I, Root, Remainder), IPos is -I, nth_integer_root_and_remainder( N, IPos, RootPos, RemainderPos), Root =:= -RootPos, Remainder =:= -RemainderPos.