Re: [Caml-list] String.map => Question to the OCaml-team

[fis@wiwi.hu-berlin.de]

Jean-Christophe Filliatre writes:
> From: Jean-Christophe Filliatre <Jean-Christophe.Filliatre@lri.fr>
> Date: Fri, 9 Apr 2004 15:29:41 +0200
> Subject: Re: [Caml-list] String.map => Question to the OCaml-team
> 
> 
>  > I don't know much about ocaml, but my bet is the implementation of
>  > strings doens't allow for anything considerably more efficient than
>  > this:
>  > 
>  > let string_map (f: char -> char) (s: string) : string =
>  >   let t = String.copy s in
>  >   let i = ref 0 in
>  >   String.iter (fun c -> let d = f c in String.set t !i d; incr i) s;
>  >   t;;
> 
> Note there is a `for' construct in ocaml:

I dislike loops...  (-:

But I am an idiot.  In this case, a loop is not only closer to how a
CPU thinks but also leads to a more elegant representation of the
algorithm.

I assume that one reason why the loop is faster is the additional
reference cell access operations in my code.  (I still think there is
some way of compiling away the reference in this particular example
using very general compiler patterns.  Not sure, though.  Perhaps I am
still an idiot.)

matthias

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