uniqueness typing

Fergus Henderson fjh@cs.mu.OZ.AU
Fri, 15 Mar 2002 20:47:49 +1100

On 12-Mar-2002, Dana Harrington <dgharrin@ucalgary.ca> wrote:
> I believe Mercury borrowed their uniqueness type (mode) system from 
> Clean.

Nope.  The support for unique modes in Mercury was developed before
we were aware of Clean.  They achieve similar aims, but it's a case
of convergent evolution, because we were both trying to solve the same
problem, rather than borrowing.  (This is in contrast to e.g. Mercury's
support for type classes, which was pretty much directly lifted from

In fact Clean's support for uniqueness is better than Mercury's.
In particular, Clean supports uniqueness polymorphism,
whereas Mercury only supports overloading on uniqueness.

Fergus Henderson <fjh@cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.