Clojure: Semi-Flattening a nested Sequence

Question

I have a list with embedded lists of vectors, which looks like:

(([1 2]) ([3 4] [5 6]) ([7 8]))

Which I know is not ideal to work with. I\'d lik

Answer 1

Also you may found useful this general 1 level flatten function I found on clojuremvc:

(defn flatten-1 
  "Flattens only the first level of a given sequence, e.g. [[1 2][3]] becomes
   [1 2 3], but [[1 [2]] [3]] becomes [1 [2] 3]."
  [seq]
  (if (or (not (seqable? seq)) (nil? seq))
    seq ; if seq is nil or not a sequence, don't do anything
    (loop [acc [] [elt & others] seq]
      (if (nil? elt) acc
        (recur
          (if (seqable? elt)
            (apply conj acc elt) ; if elt is a sequence, add each element of elt
            (conj acc elt))      ; if elt is not a sequence, add elt itself 
       others)))))

Example:

(flatten-1 (([1 2]) ([3 4] [5 6]) ([7 8])))
=>[[1 2] [3 4] [5 6] [7 8]]

concat exampe surely do job for you, but this flatten-1 is also allowing non seq elements inside a collection:

(flatten-1 '(1 2 ([3 4] [5 6]) ([7 8])))
=>[1 2 [3 4] [5 6] [7 8]]
;whereas 
(apply concat '(1 2 ([3 4] [5 6]) ([7 8])))
=> java.lang.IllegalArgumentException: 
   Don't know how to create ISeq from: java.lang.Integer