From: Pierre Weis <Pierre.Weis@inria.fr>
To: matias@k-bell.com
Cc: caml-list@inria.fr
Subject: Re: [Q] Multiple patterns in O'Caml
Date: Wed, 27 Jan 1999 15:02:49 +0100 (MET) [thread overview]
Message-ID: <199901271402.PAA15684@pauillac.inria.fr> (raw)
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
> Matías.
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.
Pierre Weis
INRIA, Projet Cristal, Pierre.Weis@inria.fr, http://cristal.inria.fr/~weis/
prev parent reply other threads:[~1999-01-27 18:28 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-01-26 18:49 Matías Giovannini
1999-01-27 14:02 ` Pierre Weis [this message]
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