Daniel-Nikpayuk_SICP-Solutions/Chapter 2/2.2/exercise-2.24/exercise.lsp
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;; Copyright 2015 Daniel Nikpayuk
;;
;; This file is part of SICP Solutions.
;;
;; SICP Solutions is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License
;; as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
;;
;; SICP Solutions is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty
;; of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License along with SICP Solutions. If not, see
;; <http://www.gnu.org/licenses/>.
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;(list 1 (list 2 (list 3 4)))

; interpreter:
;(1 (2 (3 4)))

; box-and-pointer:
; [*][*]--[*][*]--\
;  |       |
;  1      [*][*]--[*][*]--\
;          |       |
;          2      [*][*]--[*][*]--\
;                  |       |
;                  3       4

; tree:
; The first branch is '1', the second branch is a subtree '(2 (3 4))'
; Of this subtree, the first branch is '2', the second branch is subtree '(3 4)'
; Of this subtree, the first branch is '3', the second branch is the leaf '4'.

