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|
;
; Towers of Hanoi
;
; Copyright © 2016 Keith Packard <keithp@keithp.com>
;
; This program 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 2 of the License, or
; (at your option) any later version.
;
; This program 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.
;
; ANSI control sequences
(define move-to (lambda (col row)
(for-each display (list "\033[" row ";" col "H"))
)
)
(define clear (lambda ()
(display "\033[2J")
)
)
(define display-string (lambda (x y str)
(move-to x y)
(display str)
)
)
; Here's the pieces to display
(define tower '(" * " " *** " " ***** " " ******* " " ********* " "***********"))
; Here's all of the towers of pieces
; This is generated when the program is run
(define towers ())
(define 1- (lambda (x) (- x 1)))
; Display one tower, clearing any
; space above it
(define display-tower (lambda (x y clear tower)
(cond ((= 0 clear)
(cond ((not (null? tower))
(display-string x y (car tower))
(display-tower x (1+ y) 0 (cdr tower))
)
)
)
(else
(display-string x y " ")
(display-tower x (1+ y) (1- clear) tower)
)
)
)
)
; Position of the top of the tower on the screen
; Shorter towers start further down the screen
(define tower-pos (lambda (y tower)
(- y (length tower))
)
)
; Display all of the towers, spaced 20 columns apart
(define display-towers (lambda (x y towers)
(cond ((not (null? towers))
(display-tower x 0 (tower-pos y (car towers)) (car towers))
(display-towers (+ x 20) y (cdr towers)))
)
)
)
(define top 0)
; Display all of the towers, then move the cursor
; out of the way and flush the output
(define display-hanoi (lambda ()
(display-towers 0 top towers)
(move-to 1 21)
(flush-output)
)
)
; Reset towers to the starting state, with
; all of the pieces in the first tower and the
; other two empty
(define reset-towers (lambda ()
(set! towers (list tower () ()))
(set! top (+ (length tower) 3))
(length tower)
)
)
; Replace a tower in the list of towers
; with a new value
(define replace (lambda (list pos member)
(cond ((= pos 0) (cons member (cdr list)))
((cons (car list) (replace (cdr list) (1- pos) member)))
)
)
)
; Move a piece from the top of one tower
; to the top of another
(define move-delay 10)
(define move-piece (lambda (from to)
(let* ((from-tower (list-ref towers from))
(to-tower (list-ref towers to))
(piece (car from-tower)))
(set! from-tower (cdr from-tower))
(set! to-tower (cons piece to-tower))
(set! towers (replace towers from from-tower))
(set! towers (replace towers to to-tower))
(display-hanoi)
; (delay move-delay)
)
)
)
; The implementation of the game
(define _hanoi (lambda (n from to use)
(cond ((= 1 n)
(move-piece from to)
)
(else
(_hanoi (1- n) from use to)
(_hanoi 1 from to use)
(_hanoi (1- n) use to from)
)
)
)
)
; A pretty interface which
; resets the state of the game,
; clears the screen and runs
; the program
(define hanoi (lambda ()
(let ((len))
(set! len (reset-towers))
(clear)
(_hanoi len 0 1 2)
(move-to 0 23)
#t
)
)
)
|
