# gcd 0 0 = 0

**Simon Peyton-Jones
**
simonpj@microsoft.com

*Tue, 18 Dec 2001 01:38:21 -0800*

If everyone likes this I'll put it in; otherwise I'll simply state that
gcd 0 0 is defined to be 0.=20
Christoph does not like this, but the weight of world opinion seems=20
to be fairly clearly in favour of gcd 0 0 =3D 0. Let's try to wrap =
this
one
up.
Simon
|* -----Original Message-----
*|* From: Alan Bawden [mailto:Alan@LCS.MIT.EDU]=20
*|* Sent: 17 December 2001 18:45
*|* To: haskell@haskell.org; Simon Peyton-Jones
*|* Subject: Re: gcd 0 0 =3D 0
*|*=20
*|*=20
*|* From: Lars Henrik Mathiesen <thorinn@diku.dk>
*|* Date: 17 Dec 2001 14:50:21 -0000
*|* ...
*|* In case it isn't clear already, these definitions make a lattice on
*|* the positive integers, with divides ~ leq, gcd ~ meet and=20
*|* lcm ~ join,
*|* using the report's definitions of gcd and lcm.
*|*=20
*|* Indeed, that's a nice way of putting it. How about if the report just
*|* says:
*|*=20
*|* In order to make the non-negative integers into a lattice=20
*|* under `gcd'
*|* and `lcm', we define `gcd 0 0 =3D 0'.
*|*=20
*