From b3b5bd2c14cfcde6c551a87ee6da08a53f1e4bc6 Mon Sep 17 00:00:00 2001
From: Keith Packard <keithp@keithp.com>
Date: Mon, 14 Nov 2016 23:04:05 -0800
Subject: [PATCH] altos/lisp: Add license to hanoi demo

Signed-off-by: Keith Packard <keithp@keithp.com>
---
 src/test/hanoi.lisp | 68 ++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 61 insertions(+), 7 deletions(-)

diff --git a/src/test/hanoi.lisp b/src/test/hanoi.lisp
index 0c4bfca5..b84b8174 100644
--- a/src/test/hanoi.lisp
+++ b/src/test/hanoi.lisp
@@ -1,3 +1,22 @@
+;
+; 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
+
 (defun move-to (col row)
   (patom "\033[" row ";" col "H" nil)
   )
@@ -6,16 +25,25 @@
   (patom "\033[2J" nil)
   )
 
+(defun display-string (x y str)
+  (move-to x y)
+  (patom str)
+  )
+
+; Here's the pieces to display
+
 (setq stack '("*" "**" "***" "****" "*****" "******" "*******"))
 
 (setq top (+ (length stack) 3))
 
+;
+; Here's all of the stacks of pieces
+; This is generated when the program is run
+;
 (setq stacks nil)
 
-(defun display-string (x y str)
-  (move-to x y)
-  (patom str)
-  )
+; Display one stack, clearing any
+; space above it
 
 (defun display-stack (x y clear stack)
   (cond ((= 0 clear)
@@ -34,16 +62,23 @@
 	)
   )
 
+; This should probably be included in the rom image...
+
 (defun length (list)
   (cond (list (1+ (length (cdr list))))
 	(0)
 	)
   )
 
+; Position of the top of the stack on the screen
+; Shorter stacks start further down the screen
+
 (defun stack-pos (y stack)
   (- y (length stack))
   )
 
+; Display all of the stacks, spaced 20 columns apart
+
 (defun display-stacks (x y stacks)
   (cond (stacks (progn
 		  (display-stack x 0 (stack-pos y (car stacks)) (car stacks))
@@ -52,21 +87,27 @@
 	)
   )
 
+; Display all of the stacks, then move the cursor
+; out of the way and flush the output
+
 (defun display ()
   (display-stacks 0 top stacks)
   (move-to 1 21)
   (flush)
   )
 
-(defun length (l)
-  (cond (l (1+ (length (cdr l)))) (0))
-  )
+; Reset stacks to the starting state, with
+; all of the pieces in the first stack and the
+; other two empty
 
 (defun reset-stacks ()
   (setq stacks (list stack nil nil))
   (length stack)
   )
 
+; more functions which could usefully
+; be in the rom image
+
 (defun min (a b)
   (cond ((< a b) a)
 	(b)
@@ -79,12 +120,18 @@
 	)
   )
 
+; Replace a stack in the list of stacks
+; with a new value
+
 (defun replace (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 stack
+; to the top of another
+
 (defun move-piece (from to)
   (let ((from-stack (nth stacks from))
 	(to-stack (nth stacks to))
@@ -98,6 +145,8 @@
     )
   )
 
+; The implementation of the game
+
 (defun _hanoi (n from to use)
   (cond ((= 1 n)
 	 (progn
@@ -114,6 +163,11 @@
 	)
   )
 
+; A pretty interface which
+; resets the state of the game,
+; clears the screen and runs
+; the program
+
 (defun hanoi ()
   (setq len (reset-stacks))
   (clear)
-- 
2.30.2