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Date: Thu, 11 May 2000 14:59:16 -0400 (EDT)
From: Hongwei  Xi  <hwxi@ececs.uc.edu>
To: Pierre Weis <Pierre.Weis@inria.fr>
cc: caml-list@inria.fr
Subject: Re: reference initialization
In-Reply-To: <200005111358.PAA03140@pauillac.inria.fr>
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Okay, I withdraw my argument that the Java strategy is better then
the ML strategy However, I'd like to use the following example
to make my point clear.

I want to combine two arrays into one. Here is the code in OCaml.

let combine_arrays a b =
  let alen = Array.length a in
  let blen = Array.length b in
  let c = Array.make (alen + blen) ?
  in begin
    for i = 0 to alen - 1 do
      c.(i) <- a.(i)
    done;
    for i = 0 to blen -1 do
      c.(alen + i) <- b.(i)
    done
  end

Of course, you need to provide ? to make the above code work.
Here is my argument:

(1) If you try to provide ?, the code becomes repulsive.
(2) If you really want to make sure that 'c' is well-initialized,
you should probably check this after those two loops. The question
is how to incorporate the checking result into the type system.
(3) If you initialize 'c' with a (wrong) value, it seems to me
that nothing is achieved.
(4) Also, the problem cannot be solved using option type.

This is a precise senario that I had in mind, where the kind of
mandatory array initialization in ML-like langugages is simply
inappropriate, isn't it?

Cheers,

--Hongwei

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