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From: Pascal Nicolas <pn@univ-angers.fr>
Message-Id: <199506090729.JAA03487@vink.Univ-Angers.Fr>
Subject: Re: vector dot multiply
To: caml-list@pauillac.inria.fr (Liste de diffusion Caml)
Date: Fri, 9 Jun 95 9:29:41 METDST
In-Reply-To: <199506081716.NAA01690@thomas.ge.com>; from "U-E59264-Osman Buyukisik" at Jun 8, 95 1:16 pm
Mailer: Elm [revision: 70.85]
Sender: weis

> 
> Hi,
>  What would be 1). elegant
>                2). efficient  
>  way to write a "dot multiply" function in caml-light? 
> This is what I came up with but I am hoping for a better one :
> 
> let dot a b = let rec dot_aux a b i sum =
> if i< vect_length a then
>    dot_aux a b (i+1) (sum +. (a.(i) *. b.(i)) )
>  else
>    sum
> in
>  dot_aux a b 0 0.0;;
> 
In order to avoid to (re)compute the length of a at each recursive call, you
can modify a little your function as follows

 let dot a b = let rec dot_aux a b i sum L =
 if i < L then
    dot_aux a b (i+1) (sum +. (a.(i) *. b.(i))) L
 else
    sum
 in dot_aux a b 0 0.0 (vect_length a) ;;


--
Pascal NICOLAS                                       LERIA  Université d'ANGERS
Tél : (33) 41 73 54 20             2, Bd Lavoisier 49045 ANGERS cedex 01 FRANCE
E Mail : pn@univ-angers.fr
WWW Url : http://www.univ-angers.fr/~pn/nicolas.html