Re: Question regarding the creation of arrays

You can define make_matrix yourself as:

  let make_matrix m n v =
    Array.init m (fun _ -> Array.init n v)

this technique can easily be extended to arbitrary dimensions, for example:

  Array.init n1 (fun _ ->
  Array.init n2 (fun _ ->
  Array.make n v))

Note that (Array.make m (Array.make n v)) would be terribly wrong
because of aliasing: the sub-arrays of the larger array are the same,
and get modified at the same time:

# let t = Array.make 2 (Array.make 2 0);;
val t : int array array = [|[|0; 0|]; [|0; 0|]|]
# t.(0).(1) <- 1; t;;
- : int array array = [|[|0; 1|]; [|0; 1|]|]

This is why Array.init, which recompute a fresh sub-array for each
index, should be used instead.

On Tue, Jul 22, 2014 at 6:10 AM, Nicolas FRANCOIS
[email protected] [ocaml_beginners]
<[email protected]> wrote:
> Hi.
>
> To create a fresh one dimmension array, we use Array.create. For 2
> dimensions, we can use Array.make_matrix.
>
> What is the general construction for a 3 or more dimensions array ?
>
> Thanks for your answers.
>
> \bye
>
> --
>
> Nicolas FRANCOIS                      |  /\
> http://nicolas.francois.free.fr       | |__|
>                                       X--/\\
> We are the Micro$oft.                   _\_V
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> You will be assimilated.         darthvader penguin
>
>
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> Posted by: Nicolas FRANCOIS <[email protected]>
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