From: Jung K Oh
Subject: Re: Looking for a Rexursive function to count a height of tree
Date: Fri, 14 Oct 1994 22:18:50 +0000
Message-ID: <37n04a$kr8@news.uncc.edu>

Summary: 
Keywords: 

Is anybody out there to help me make a program that count a height of tree.
For example,

> (function '(a b c d))
 0
> (function '(a (b c) d))
 1
> (function '(a (b (c) d )))
 2
> (function '((a b c) d))
 nil   ----> since not tree 

• Re: Looking for a Rexursive function to count a height of tree Barry Margolin
• Re: Looking for a Rexursive function to count a height of tree Simon Brooke

From: Barry Margolin
Subject: Re: Looking for a Rexursive function to count a height of tree
Date: Sat, 15 Oct 1994 22:44:07 +0000
Message-ID: <37plvn$1in@tools.near.net>

In article <··········@news.uncc.edu> ····@uncc.edu writes:
>Is anybody out there to help me make a program that count a height of tree.

I hope this isn't a homework assignment.

>For example,
>
>> (function '(a b c d))
> 0

I would call that a tree of height 1.  An atom would be a tree of height 0.

>> (function '((a b c) d))
> nil   ----> since not tree 

It looks like a tree to me.  In fact, *everything* in Lisp is a tree, since
an atom is just the degenerative case of a tree containing one node.

(defun tree-height (tree)
  (if (atom tree) 0
      (1+ (reduce #'max (mapcar #'tree-height tree)))))
-- 

Barry Margolin
BBN Internet Services Corp.
······@near.net

From: Simon Brooke
Subject: Re: Looking for a Rexursive function to count a height of tree
Date: Tue, 18 Oct 1994 07:14:34 +0000
Message-ID: <CxuxGC.125@rheged.dircon.co.uk>

In article <··········@news.uncc.edu> ····@uncc.edu (Jung K Oh) writes:

   Is anybody out there to help me make a program that count a height of tree.
   For example,

   > (function '(a b c d))
    0
   > (function '(a (b c) d))
    1
   > (function '(a (b (c) d )))
    2
   > (function '((a b c) d))
    nil   ----> since not tree 

So many firstyear students seem to have been given this problem as
homework that I thought I'd post the solution to give us all some
peace. I do not intend to do anybody else's homework in future,
however.

(i) All your examples are trees. Any SExpr is a tree.

(2) The following is XLISP. You should check before submitting it as
homework to a course taught either in Common LISP or scheme.

(defun treeheight (form)
  (cond ((null form) 0)
	((atom form) 0)
	(t (apply 'max (mapcar  
			  '(lambda (elt)
			     (cond ((consp elt) (1+ (treeheight elt)))
				   (t 0))) form)))))




-- 
---------------
"There is no point in making further promises now about reducing
taxation: nobody believes us." Edward Heath, October 1994