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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.122The 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.