paper announcement

The following paper is available by anonymous ftp at ftp.dm.unibo.it 
(Dipartimento di Matematica of the University of Bologna, Italy).
The paper, in compressed postscript form, is in the directory pub/asperti,
and it is called acta.ps.Z. It is going to appear in a special issue
of ACTA INFORMATICAE, devoted to Categories in Computer Science.

In you like to play with an optimal (?!) compiler of lambda terms,
in the same directory you will find a prototype, very preliminary
(but running) version, in the file opt_impl.tar.Z (compressed, tar

						-- andrea


			Andrea Asperti
	Dipartimento di Matematica, Universit\'a di Bologna,
	   P.za di Porta S.Donato, 40126 Bologna, ITALY.

The paper discusses, in a categorical perspective, some recent works
on optimal graph reduction techniques for the lambda-calculus.  In
particular, we relate the two "brackets" of Gonthier-Abadi-Levy (POPL
92, LICS 92) to the two operations associated with the comonad "!" of
Linear Logic.  The rewriting rules can be then understood as a "local
implementation" of naturality laws, that is as the broadcasting of
some information from the output to the inputs of a term, following
its connected structure.