Synthesize smallest map satisfying featurec constraints in core.logic?

Question

In core.logic, is there a way to translate the outputs of a program like

(run 2 [q]
  (fresh [a]
    (featurec q {:foo a})
    (membero a '(5))
    (conde 
      ((featurec q {:bar 2}))
      ((featurec q {:baz 2})))))

into the smallest maps that satisfy each solution's constraints, in this case {:foo 5, :bar 2} and {:foo 5, :baz 2}?

Why use featurec when the minimal set of keys is already known? Why not (== q {:foo a :bar 2})? — Taylor Wood
In a more complex (potentially even recursive) relation, some featurec clauses might appear only in some solutions; e.g., conde clauses that each introduce different featurec constraints. I've updated the question to give an example of this. — Alex Lew

akond akond · Accepted Answer · 2018-09-25T10:20:02

You could try this, which is a bit complicated, but it does the job.

(->> (run 1 [q]
              (fresh [l1 l2 a]
                     (membero a '(5))
                     (emptyo l1)
                     (conso [:foo a] l1 l2)
                     (conso [:bar 2] l2 q)))
         (first)
         (into {}))

or

(run 1 [q]
         (fresh [a B]
                (membero a '(5))
                (== B 2)
                (== q {:foo a :bar B})))

I am sure that William Byrd can do better.

Synthesize smallest map satisfying featurec constraints in core.logic?

1 Answers