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[Caml-list] New to OCaml: can someone explain how this code can be done better?
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 Date: 2001-06-23 (05:27) From: Jeremy Fincher Subject: [Caml-list] New to OCaml: can someone explain how this code can be done better?
```Since I'm learning OCaml, I've been writing little functions as I get a
grasp on each little bit of the syntax.  One of these functions is
"permute", which takes a string and returns a list of all the permutations
of the string.  Here's the function:

let rec permute_rec f s =
if String.length s = 1 then
(f ^ s) :: []
else
let l = ref [] in
for i = 0 to ((String.length s) - 1) do
let c = String.sub s i 1 in
let rem = (String.sub s 0 i) ^ ((String.sub s (i+1) ((String.length
s)-i-1))) in
l := (List.append !l (permute_rec (f^c) rem))
done;
!l;;

let permute = permute_rec "";;

Now, I'm sure this isn't the best way to code that function.  What I'm
hoping is that someone can show me a few things about the function: how to
make it tail recursive; a better (less imperative?) method of writing it,
and which parts are not consistent with common/standard OCaml idiom.
*Anything* I'm shown should at least help me learn, so if you have any
comments/opinions, please tell me!

Thanks,
Jeremy
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