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Date: Thu, 28 Jun 2001 08:47:09 +0200
From: Judicaël Courant <Judicael.Courant@lri.fr>
To: Chris Hecker <checker@d6.com>
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] there has to be a better way to write this code
Message-Id: <20010628084709.201e7770.Judicael.Courant@lri.fr>
In-Reply-To: <200106280300.UAA18698@smtp4-cm.mail.eni.net>
References: <200106280300.UAA18698@smtp4-cm.mail.eni.net>
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Hi,

On Wed, 27 Jun 2001 20:00:27 -0700
Chris Hecker <checker@d6.com> wrote:

> 
> My problem is that the attached code is really pretty verbose and
> redundant.  Each of the get_* functions has a lot of duplicate code in
> it, and I think there must be a better way.  I'd like to write
> something like this (not really caml syntax, but you get the idea):
> 
> let get_float h s = get_meta h s (Float el -> el)
> 

let get_float h s = get_meta h s (fun (Float el) -> el)

is legal syntax, but IMHO

let get_float h s = get_meta h s (fun x -> match x with Float el -> el | _
-> Not_found)

would be a bit cleaner

Now, what about this for get_meta:

let get_meta h s f =
  let g x = try ignore (f x); true with _ -> false in
  let s = List.find g (Hashtbl.find_all h s) in
  f s
 ;;

Or, if you do not want to apply f twice to its argument, you can rewrite
find to better suit your needs.

The original code is
let rec find p = function
  | [] -> raise Not_found
  | x :: l -> if p x then x else find p l

I suggest:
let rec find_and_apply p = function
  | [] -> raise Not_found
  | x :: l -> try p x with _ -> find_and_apply p l

Then, you can write
let get_meta h s f = find_and_apply f (Hashtbl.find_all h s)

Hope this helps...

Judicaël.
-- 
Judicael.Courant@lri.fr, http://www.lri.fr/~jcourant/
(+33) (0)1 69 15 64 85
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