/usr/share/swi-prolog/pack/clpBNR/prolog/clpBNR.pl
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 range(?X, ?Bs:number_list) is semidet
Succeeds if X is numeric and Bs unifies with a list containing the lower and upper bound of X; otherwise fails. If X is a logic variable range(X,[2,3]) is equivalent to X::real(2,3). If X is a number the lower and upper bounds are the same. Examples: 
?- X::integer(1,10), range(X,Bs).
Bs = [1, 10],
X::integer(1, 10).

?- range(42,Bs).
Bs = [42, 42].

?- range(X,[2,3]).
X::real(2, 3).