some secondᵒ magic

secondo.hy

(import [adderall.dsl [*]])
(require adderall.dsl)

(defreader t [expr] `(, ~@expr))

(defn secondᵒ [l x]
  (fresh [r]
    (restᵒ l r)
    (firstᵒ r x)))

(run* [q]
  (fresh (x y)
    (appendᵒ x y ["a" "b" "c" "d"])
      (condᵉ
        [(firstᵒ y "c")]
        [(secondᵒ y "c")])
    (≡ #t(x y) q)))

;; [(['a'], ['b', 'c', 'd']),
;; (['a', 'b'], ['c', 'd'])]

FYI, you don't need the #t reader macro, you can just write (≡ (, x y) q).