Daniel-Nikpayuk_SICP-Solutions/Chapter 3/3.3/exercise-3.16/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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;counts |.|/| as a pair:
(define (count-pairs x)
  (if (not (pair? x))
      0
      (+ (count-pairs (car x))
         (count-pairs (cdr x))
         1)))

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;; So all these functional/iterative/list algorithms I've learned are all of a sudden useless? Haha.

(define x0 (list 0))
(define x1 (cons 1 x0))
(define x2 (cons 2 x1))
(count-pairs x2)
;3

(define x0 (list 0))
(define x1 (cons x0 x0))
(define x2 (cons 2 x1))
(count-pairs x2)
;4

(define x0 (list 0))
(define x1 (cons x0 x0))
(define x2 (cons x1 x1))
(count-pairs x2)
;7

(define x0 (list 0))
(set-cdr! x0 x0)
(count-pairs x0)

