hanoi.py

reduced python source for embedded apps

# Animated Towers of Hanoi using Tk with optional bitmap file in
# background.
#
# Usage: tkhanoi [n [bitmapfile]]
#
# n is the number of pieces to animate; default is 4, maximum 15.
#
# The bitmap file can be any X11 bitmap file (look in
# /usr/include/X11/bitmaps for samples); it is displayed as the
# background of the animation.  Default is no bitmap.

# This uses Steen Lumholt's Tk interface
from Tkinter import *


# Basic Towers-of-Hanoi algorithm: move n pieces from a to b, using c
# as temporary.  For each move, call report()
def hanoi(n, a, b, c, report):
	if n <= 0: return
	hanoi(n-1, a, c, b, report)
	report(n, a, b)
	hanoi(n-1, c, b, a, report)


# The graphical interface
class Tkhanoi:

	# Create our objects
	def __init__(self, n, bitmap = None):
		self.n = n
		self.tk = tk = Tk()
		self.canvas = c = Canvas(tk)
		c.pack()
		width, height = tk.getint(c['width']), tk.getint(c['height'])

		# Add background bitmap
		if bitmap:
			self.bitmap = c.create_bitmap(width/2, height/2,
						      bitmap=bitmap,
						      foreground='blue')

		# Generate pegs
		pegwidth = 10
		pegheight = height/2
		pegdist = width/3
		x1, y1 = (pegdist-pegwidth)/2, height*1/3
		x2, y2 = x1+pegwidth, y1+pegheight
		self.pegs = []
		p = c.create_rectangle(x1, y1, x2, y2, fill='black')
		self.pegs.append(p)
		x1, x2 = x1+pegdist, x2+pegdist
		p = c.create_rectangle(x1, y1, x2, y2, fill='black')
		self.pegs.append(p)
		x1, x2 = x1+pegdist, x2+pegdist
		p = c.create_rectangle(x1, y1, x2, y2, fill='black')
		self.pegs.append(p)
		self.tk.update()

		# Generate pieces
		pieceheight = pegheight/16
		maxpiecewidth = pegdist*2/3
		minpiecewidth = 2*pegwidth
		self.pegstate = [[], [], []]
		self.pieces = {}
		x1, y1 = (pegdist-maxpiecewidth)/2, y2-pieceheight-2
		x2, y2 = x1+maxpiecewidth, y1+pieceheight
		dx = (maxpiecewidth-minpiecewidth) / (2*max(1, n-1))
		for i in range(n, 0, -1):
			p = c.create_rectangle(x1, y1, x2, y2, fill='red')
			self.pieces[i] = p
			self.pegstate[0].append(i)
			x1, x2 = x1 + dx, x2-dx
			y1, y2 = y1 - pieceheight-2, y2-pieceheight-2
			self.tk.update()
			self.tk.after(25)

	# Run -- never returns
	def run(self):
		while 1:
			hanoi(self.n, 0, 1, 2, self.report)
			hanoi(self.n, 1, 2, 0, self.report)
			hanoi(self.n, 2, 0, 1, self.report)
			hanoi(self.n, 0, 2, 1, self.report)
			hanoi(self.n, 2, 1, 0, self.report)
			hanoi(self.n, 1, 0, 2, self.report)

	# Reporting callback for the actual hanoi function
	def report(self, i, a, b):
		if self.pegstate[a][-1] != i: raise RuntimeError # Assertion
		del self.pegstate[a][-1]
		p = self.pieces[i]
		c = self.canvas

		# Lift the piece above peg a
		ax1, ay1, ax2, ay2 = c.bbox(self.pegs[a])
		while 1:
			x1, y1, x2, y2 = c.bbox(p)
			if y2 < ay1: break
			c.move(p, 0, -1)
			self.tk.update()

		# Move it towards peg b
		bx1, by1, bx2, by2 = c.bbox(self.pegs[b])
		newcenter = (bx1+bx2)/2
		while 1:
			x1, y1, x2, y2 = c.bbox(p)
			center = (x1+x2)/2
			if center == newcenter: break
			if center > newcenter: c.move(p, -1, 0)
			else: c.move(p, 1, 0)
			self.tk.update()

		# Move it down on top of the previous piece
		pieceheight = y2-y1
		newbottom = by2 - pieceheight*len(self.pegstate[b]) - 2
		while 1:
			x1, y1, x2, y2 = c.bbox(p)
			if y2 >= newbottom: break
			c.move(p, 0, 1)
			self.tk.update()

		# Update peg state
		self.pegstate[b].append(i)


# Main program
def main():
	import sys, string

	# First argument is number of pegs, default 4
	if sys.argv[1:]:
		n = string.atoi(sys.argv[1])
	else:
		n = 4

	# Second argument is bitmap file, default none
	if sys.argv[2:]:
		bitmap = sys.argv[2]
		# Reverse meaning of leading '@' compared to Tk
		if bitmap[0] == '@': bitmap = bitmap[1:]
		else: bitmap = '@' + bitmap
	else:
		bitmap = None

	# Create the graphical objects...
	h = Tkhanoi(n, bitmap)

	# ...and run!
	h.run()


# Call main when run as script
if __name__ == '__main__':
	main()