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Predicate select_dict/3
Availability:built-in
[semidet]select_dict(+Select, +From, -Rest)
True when the tags of Select and From have been unified, all keys in Select appear in From and the corresponding values have been unified. The key-value pairs of From that do not appear in Select are used to form an anonymous dict, which is unified with Rest. For example: 
?- select_dict(P{x:0, y:Y}, point{x:0, y:1, z:2}, R).
P = point,
Y = 1,
R = _{z:2}.

See also :</2 to ignore Rest and >:</2 for a symmetric partial unification of two dicts.

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Imre Kilián said (2020-02-28T08:31:38):0 upvotes 0 0 downvotes
Picture of user Imre Kilián.
  1. See the last line! There is no select_dict/2 predicate, neither documented nor implemented... (should we? straightforward)
  2. I tested, if select_dict/3 works recoursively, but not... A deeper question is, if embedded dicts are foreseen at all? (IMHO: for dicts as key values, not a Prolog unification, but a further select_dict should be performed... maybe only for :</2 ?) yours: Imre