Re: [Caml-list] Re: "ocaml_beginners"::[] string to list

[Michal Moskal <malekith@pld-linux.org>]

On Mon, Feb 17, 2003 at 02:53:07PM -0800, Issac Trotts wrote:
> Christian Schaller wrote:
> 
> >Hi everyone!
> >
> >I'm trying to find a built in function for converting a string to a list of
> >characters, similar to SML's explode.  Is something like this available?
> >
> >Thank you!
> >
> >- Chris
> >
> # let explode s =
>   let n = String.length s in
>   let rec aux k = if k = n then [] else s.[k] :: aux (k+1) in
>   aux 0;;
>      val explode : string -> char list = <fun>
> # explode "foo";;
> - : char list = ['f'; 'o'; 'o']

Not tail recursive :)

>From my patch to pleac (http://pleac.sourceforge.net):

(* convert string to list of chars *)
let explode s =
  let rec f acc = function
    | -1 -> acc
    | k -> f (s.[k] :: acc) (k - 1)
  in f [] (String.length s - 1)

(* convert list of chars to string *)
let implode l =
  let s = String.create (List.length l) in
  let rec f n = function
    | x :: xs -> s.[n] <- x; f (n + 1) xs
    | [] -> s
  in f 0 l

PS: I know, it doesn't matter much if it's tail recursive or not, nobody
is going to use for data of size when it matters :-)

-- 
: Michal Moskal ::::: malekith/at/pld-linux.org :  GCS {C,UL}++++$ a? !tv
: PLD Linux ::::::: Wroclaw University, CS Dept :  {E-,w}-- {b++,e}>+++ h
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