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#!/home/keithp/bin/ao-scheme
;
; 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 col row)
(for-each display (list "\033[" row ";" col "H"))
)
(define (clear)
(display "\033[2J")
)
(define (display-string x y str)
(move-to x y)
(display str)
)
(define (make-piece num max)
; A piece for position 'num'
; is num + 1 + num stars
; centered in a field of max *
; 2 + 1 characters with spaces
; on either side. This way,
; every piece is the same
; number of characters
(define (chars n c)
(if (zero? n) ""
(+ c (chars (- n 1) c))
)
)
(+ (chars (- max num 1) " ")
(chars (+ (* num 2) 1) "*")
(chars (- max num 1) " ")
)
)
(define (make-pieces max)
; Make a list of numbers from 0 to max-1
(define (nums cur max)
(if (= cur max) ()
(cons cur (nums (+ cur 1) max))
)
)
; Create a list of pieces
(map (lambda (x) (make-piece x max)) (nums 0 max))
)
; Here's all of the towers of pieces
; This is generated when the program is run
(define towers ())
; position of the bottom of
; the stacks set at runtime
(define bottom-y 0)
(define left-x 0)
(define move-delay 25)
; Display one tower, clearing any
; space above it
(define (display-tower x y clear tower)
(cond ((= 0 clear)
(cond ((not (null? tower))
(display-string x y (car tower))
(display-tower x (+ y 1) 0 (cdr tower))
)
)
)
(else
(display-string x y " ")
(display-tower x (+ y 1) (- clear 1) tower)
)
)
)
; Position of the top of the tower on the screen
; Shorter towers start further down the screen
(define (tower-pos tower)
(- bottom-y (length tower))
)
; Display all of the towers, spaced 20 columns apart
(define (display-towers x towers)
(cond ((not (null? towers))
(display-tower x 0 (tower-pos (car towers)) (car towers))
(display-towers (+ x 20) (cdr towers)))
)
)
; Display all of the towers, then move the cursor
; out of the way and flush the output
(define (display-hanoi)
(display-towers left-x towers)
(move-to 1 23)
(flush-output)
(delay move-delay)
)
; Reset towers to the starting state, with
; all of the pieces in the first tower and the
; other two empty
(define (reset-towers len)
(set! towers (list (make-pieces len) () ()))
(set! bottom-y (+ len 3))
)
; Move a piece from the top of one tower
; to the top of another
(define (move-piece from to)
; references to the cons holding the two towers
(define from-tower (list-tail towers from))
(define to-tower (list-tail towers to))
; stick the car of from-tower onto to-tower
(set-car! to-tower (cons (caar from-tower) (car to-tower)))
; remove the car of from-tower
(set-car! from-tower (cdar from-tower))
)
; The implementation of the game
(define (_hanoi n from to use)
(cond ((= 1 n)
(move-piece from to)
(display-hanoi)
)
(else
(_hanoi (- n 1) from use to)
(_hanoi 1 from to use)
(_hanoi (- n 1) use to from)
)
)
)
; A pretty interface which
; resets the state of the game,
; clears the screen and runs
; the program
(define (hanoi len)
(reset-towers len)
(clear)
(display-hanoi)
(_hanoi len 0 1 2)
#t
)
(unless (null? (command-line)) (hanoi 6))
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