Path: utzoo!attcan!uunet!mcsun!ukc!warwick!nott-cs!piaggio!anw
From: anw@maths.nott.ac.uk (Dr A. N. Walker)
Newsgroups: comp.lang.misc
Subject: Re: C's sins of commission
Message-ID: <1990Oct15.175924.14455@maths.nott.ac.uk>
Date: 15 Oct 90 17:59:24 GMT
References: <1990Oct10.101527.2247@maths.nott.ac.uk> <1990Oct10.195202.2340@d.cs.okstate.edu>
Reply-To: anw@maths.nott.ac.uk (Dr A. N. Walker)
Organization: Maths Dept., Nott'm Univ., UK.
Lines: 25

In article <1990Oct10.195202.2340@d.cs.okstate.edu> norman@d.cs.okstate.edu
(Norman Graham) writes:
>[...]					    you may want to read this
>Miranda definition of a 3-ary tree (just to be different).

	I keep trying to get interested in Miranda, but "they" want real
money for it, which is bad news for a Maths Dept.

>  three_tree ::= Leaf num | Node int three_tree three_tree three_tree

	Well, that's fine for an acyclic structure [though not the way
I usually *think* of trees] and a lazy evaluator, but it doesn't make
sense to me in the form

	three_graph ::= Node int three_graph three_graph three_graph

Where does it all end, even lazily?  How do I express the identity of
one node with another [ie, perhaps the same node, but reached via some
chain of edges]?  How do I *draw* it?  What is *anyone*'s objection to

	MODE NODE = STRUCT (INT info, REF NODE left, right, middle) ?

-- 
Andy Walker, Maths Dept., Nott'm Univ., UK.
anw@maths.nott.ac.uk