Utility functions for Clojure's core.logic that can unwrap or flatten an arbitrarily deeply nested list (or list of lists).

flatteno.clj

(ns core.logic.util.flatteno
  (:require [clojure.core.logic :as cl]))

(cl/defna unwrapo
  "Unwrapps an arbitrarily deeply nested list"
  [l o]
  ([[e] o]
   (unwrapo e o))
  ([[f . r] o]
   (cl/conso f r o)))

(comment
  (cl/run* [q] (unwrapo [1] q))
  (cl/run* [q] (unwrapo [[1]] q))
  (cl/run* [q] (unwrapo [[[1]]] q))
  (cl/run* [q] (unwrapo [[['([1])]]] q))
  (cl/run* [q] (unwrapo [[[1 2]]] q))
  )

(cl/defna flatteno
  "Flattens a list of lists 'l' into 'o'"
  [l o]
  ([[f . r] o]
   (cl/fresh [uf fuf fr]
             (unwrapo f uf)
             (flatteno uf fuf)
             (flatteno r fr)
             (cl/appendo fuf fr o)))
  ([l o]
   (unwrapo l o)))

(comment
  (cl/run* [q] (flatteno [1] q))
  (cl/run* [q] (flatteno [[1]] q))
  (cl/run* [q] (flatteno [[[1]]] q))
  (cl/run* [q] (flatteno [[1 2]] q))
  (cl/run* [q] (flatteno [[1] [2]] q))
  (cl/run* [q] (flatteno [[1 2] [3 4]] q))
  (cl/run* [q] (flatteno [[1] [2] [3]] q))
  (cl/run* [q] (flatteno [[1 2] [3] [4 5 6]] q))
  )