54 lines
1.8 KiB
Scheme
54 lines
1.8 KiB
Scheme
;;; Copyright (C) Peter McGoron 2024
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;;; This program is free software: you can redistribute it and/or modify
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;;; it under the terms of the GNU General Public License as published by
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;;; the Free Software Foundation, version 3 of the License.
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;;;
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;;; This program is distributed in the hope that it will be useful,
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;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with this program. If not, see <https://www.gnu.org/licenses/>.
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;;; Singly linked list with tail pointer, message passing style.
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;;;
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;;; LINKED-LIST:
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;;;
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;;; (PUSH! VAL): Pushes a value to the head of the list.
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;;; (PUSH-TAIL! VAL): Pushes a value to the end of the list.
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;;; (SET-CDR! VAL): Set the cdr of TAIL to VAL. This will be overrwitten
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;;; if PUSH-TAIL! is called again.
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;;; (TO-LIST): Returns a list structure.
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(define linked-list:new
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(lambda ()
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(letrec
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((head '())
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(tail '())
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(this
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(object/immutable-attributes
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'push!
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(lambda (val)
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(set! head (cons val head))
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(if (null? tail)
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(set! tail head))
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this)
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'push-tail!
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(lambda (val)
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(if (null? tail)
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(this 'push! val)
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(begin
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(set-cdr! tail (cons val '()))
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(set! tail (cdr tail))))
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this)
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'set-cdr!
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(lambda (val)
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(if (null? tail)
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(error "cannot set cdr of empty list")
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(set-cdr! tail val))
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this)
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'to-list
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(lambda () head))))
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this)))
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