From: Pierre Weis <Pierre.Weis@inria.fr>
Subject: Re: [Q] Multiple patterns in O'Caml
Date: Wed, 27 Jan 1999 15:02:49 +0100 (MET)
In-Reply-To: <36AE0E34.6BF3A367@k-bell.com> from "=?iso-8859-1?Q?Mat=EDas?= Giovannini" at Jan 26, 99 03:49:28 pm
> (* In O'Caml *)
> let rec drop n l = match (n,l) with
> | 0,l -> l
> | n, -> failwith "drop"
> | n,a::x -> drop (pred n) x
> but this requires an extraneous tuple construction and its subsequent
> destruction, and kinda seems wasteful to me.
> Thank you in advance, best regards
There is no spurious construction of tuples nor subsequent destuction
when matching an immediate tuple: this is optimised by the compiler of
Objective Caml. This way you can consider writing
match x, y, z with
| 1, 2, 3 -> ...
as a syntactic notation for ``parallel matching'', or matching of more
than one value at a time.
INRIA, Projet Cristal, Pierre.Weis@inria.fr, http://cristal.inria.fr/~weis/
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