How to remove double parentheses and leave only the nested lists in lisp?

Question

For example, convert from this:

((((7 8) (0 H 0))) (((11 12))))

to the following:

((7 8) (0 H 0) (11 12))

not (7 8 0 H 0 11 12) !! Thank you.

http://stackoverflow.com/questions/39071217/every-second-bracket-lisp — Rainer Joswig, Aug 22 '16 at 13:19
Possible duplicate of [How to remove nested parentheses in LISP](http://stackoverflow.com/questions/2680864/how-to-remove-nested-parentheses-in-lisp) — Tim B, Aug 22 '16 at 13:58
No it is not a duplicate, and the first one is not answered :) — Ивана Ристова, Aug 23 '16 at 09:36

score 0 · Answer 1 · answered Aug 22 '16 at 13:42

0: (MYSTERIOUS ((((7 8) (0 H 0))) (((11 12))) (((A B) (C D))) ((D E F))))
  1: (MAGIC (((7 8) (0 H 0))))
    2: (MAGIC ((7 8) (0 H 0)))
      3: (MAGIC (7 8))
      3: MAGIC returned ((7 8))
      3: (MAGIC (0 H 0))
      3: MAGIC returned ((0 H 0))
    2: MAGIC returned ((7 8) (0 H 0))
  1: MAGIC returned ((7 8) (0 H 0))
  1: (MAGIC (((11 12))))
    2: (MAGIC ((11 12)))
      3: (MAGIC (11 12))
      3: MAGIC returned ((11 12))
    2: MAGIC returned ((11 12))
  1: MAGIC returned ((11 12))
  1: (MAGIC (((A B) (C D))))
    2: (MAGIC ((A B) (C D)))
      3: (MAGIC (A B))
      3: MAGIC returned ((A B))
      3: (MAGIC (C D))
      3: MAGIC returned ((C D))
    2: MAGIC returned ((A B) (C D))
  1: MAGIC returned ((A B) (C D))
  1: (MAGIC ((D E F)))
    2: (MAGIC (D E F))
    2: MAGIC returned ((D E F))
  1: MAGIC returned ((D E F))
0: MYSTERIOUS returned ((7 8) (0 H 0) (11 12) (A B) (C D) (D E F))

@Sylwester `(flatten '((((7 8) (0 H 0))) (((11 12)))))` gives `(7 8 0 H 0 11 12)`, which is different from the (possibly underspecified) problem. — coredump, Aug 23 '16 at 05:19

score 0 · Answer 2 · answered Aug 23 '16 at 11:49

0

if the nesting level is constant, like in the example, you could simply do this:

CL-USER> (mapcan #'car '((((7 8) (0 H 0))) (((11 12)))))
((7 8) (0 H 0) (11 12))

answered Aug 23 '16 at 11:49

leetwinski

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You are mutating constant values. You have no guarantee what's going to happen. – Sylwester Aug 26 '16 at 22:15
should i copy the car instead? `(mapcan (lambda (x) (copy (car x))) ...)` or something else? – leetwinski Aug 26 '16 at 23:08

How to remove double parentheses and leave only the nested lists in lisp?

2 Answers2