/usr/share/swi-prolog/pack/clpBNR/prolog/clpBNR.pl
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 interval_degree(?X:numeric, ?N:integer) is semidet
Succeeds if X is numeric and N = number of clpBNR constraints on X; otherwise fails. If X is a number, N = 0. Examples: 
?- {X==Y+1}, interval_degree(X,N).
N = 1,
X::real(-1.0Inf, 1.0Inf),
Y::real(-1.0Inf, 1.0Inf).

?- interval_degree(42,N).
N = 0.