:- object(integer,
extends(number)).
:- info([
version is 1.0,
author is 'Paulo Moura',
date is 2000/7/24,
comment is 'Integer data type predicates.']).
:- public(between/3).
:- mode(between(+integer, +integer, ?integer), zero_or_more).
:- info(between/3, [
comment is 'Returns integers in the interval defined by the two first arguments.',
argnames is ['Lower', 'Upper', 'Integer']]).
between(Lower, Upper, Integer) :-
integer(Lower),
integer(Upper),
(var(Integer) ->
Lower =< Upper,
generate(Lower, Upper, Integer)
;
integer(Integer),
Lower =< Integer,
Integer =< Upper).
generate(Lower, _, Lower).
generate(Lower, Upper, Integer) :-
Lower < Upper,
Next is Lower + 1,
generate(Next, Upper, Integer).
valid(Integer) :-
integer(Integer).
:- end_object.
