[Caml-list] beginner needs help creating a dynamically resizable array

[Caml-list] beginner needs help creating a dynamically resizable array

[Ram Bhamidipaty]

I am trying to create a dynamically resizable array. So far this is what I have:

type 'a darray = {
    mutable size_of_buf : int;
    mutable num_in_buf : int;
    mutable buf : 'a array;
  }
;;

let create t = { size_of_buf=20; num_in_buf=0; buf = Array.make 20 t; }
;;

I want to create a function that can resize this array. I want the
function to look something like this:

let resize dyn_array_ref new_size =
  
;;

The function resize should table a reference to a darray record, and
an int that specifies the new desired size of the array. There should
be no return value.

The problem I am running into is that I don't know how to create a new
larger array of the same time as the original array. The only two
choices that I can think of are: 1. Somehow store the type of the
array in the record or 2. Somehow get the array element type from the
"buf" array in the record.

Unfortunately I have no idea about how to do either 1 or 2.

I know there is atleast one package/module that provides this
functionality. But I don't want to use someone elses code - I am
trying to learn OCaml and I think this would be a good thing to do
with my own code.

Any help will be appreciated.
-Ram

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Re: [Caml-list] beginner needs help creating a dynamically resizable array

[Michal Moskal]

On Wed, Oct 01, 2003 at 10:59:18PM -0700, Ram Bhamidipaty wrote:
> I am trying to create a dynamically resizable array. 
[...]
> let resize dyn_array_ref new_size =
[...]
> The problem I am running into is that I don't know how to create a new
> larger array of the same time as the original array. The only two
> choices that I can think of are: 1. Somehow store the type of the
> array in the record or 2. Somehow get the array element type from the
> "buf" array in the record.
> 
> Unfortunately I have no idea about how to do either 1 or 2.

You can fill your array with *value* buf.{0}. You don't need its
type. This will present some odds for the GC, but if it's for educational
purposes then it's OK. The other way is Obj.magic trickery...

> I know there is atleast one package/module that provides this
> functionality. But I don't want to use someone elses code - I am
> trying to learn OCaml and I think this would be a good thing to do
> with my own code.

...and for this reason I personally don't think it's best example to
learn OCaml on.

-- 
: Michal Moskal :: http://www.kernel.pl/~malekith : GCS {C,UL}++++$ a? !tv
: When in doubt, use brute force. -- Ken Thompson : {E-,w}-- {b++,e}>+++ h

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Re: [Caml-list] beginner needs help creating a dynamically resizable array

[Nicolas Cannasse]

> I am trying to create a dynamically resizable array. So far this is what I
have:
[...]

You can use DynArray from the ExtLib :
http://sourceforge.net/projects/ocaml-lib

Nicolas Cannasse

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Re: [Caml-list] beginner needs help creating a dynamically resizable array

[Markus Mottl]

On Wed, 01 Oct 2003, Ram Bhamidipaty wrote:
> I am trying to create a dynamically resizable array. So far this is what I have:

You might want to try the RES-library:

  http://www.oefai.at/~markus/home/ocaml_sources.html#RES

Regards,
Markus Mottl

-- 
Markus Mottl          http://www.oefai.at/~markus          markus@oefai.at

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