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To: caml-list@inria.fr
Subject: Re: [Caml-list] Great Beginner
References: <3BEBDDCA.1060307@francetelecom.com>
From: Remi VANICAT <vanicat@labri.u-bordeaux.fr>
Date: 11 Nov 2001 12:34:28 +0100
In-Reply-To: <3BEBDDCA.1060307@francetelecom.com>
Message-ID: <87hes1tubf.dlv@wanadoo.fr>
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Franck <franck.collineau@francetelecom.com> writes:

> Hi!
> 
> I want to calculate the sum of the n first numbers.
> I've written this code:
> let x =0;;
> let somme n =
>         for i=1 to n
>                 do
>                   x=x+i
>                 done;;
> 
> It doesn't work.
> Why ?

Because ocaml is a functional language, so imperative action (as x = x
+ i) doesn't work.

A mean to do this is :
let x = ref 0;;
let somme n =
  for i = 1 to n do
    x := !x + i
  done;;

but the good way to do it is more :
let rec somme n =
  if n = 0 then 0
  else n + (somme (n - 1))

let x = somme 10

or even better (with a tail recursive function) :

let somme n =
  let rec aux i x =
    if i <= n then
      aux (i+1) (x + i)
    else x in
  aux 1 0


-- 
Rémi Vanicat
vanicat@labri.u-bordeaux.fr
http://dept-info.labri.u-bordeaux.fr/~vanicat
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