From: Jean-Christophe Filliatre <filliatr@lri.fr>
To: "Alexander A. Vlasov" <zulu@galaradio.com>
Cc: caml-list@yquem.inria.fr
Subject: Re: [Caml-list] Beginner's question.
Date: Thu, 27 Oct 2005 15:50:05 +0200 [thread overview]
Message-ID: <17248.56077.589928.491952@gargle.gargle.HOWL> (raw)
In-Reply-To: <1130419808.12902.13.camel@localhost.localdomain>
Alexander A. Vlasov writes:
> I'm making my first steps in OCaml and trying (just for expirience) to
> implement a simple function which applies given function to all elements
> of given list.
>
> But I can't do it using pattern matching -- following function doesn't
> work
>
> let rec mapm func lst = function
> | ( _, [] ) -> []
> | ( _, head::tail ) -> (func head) :: (mapm func tail)
"function" defines a function over an anonymous argument which is
immediatly filtered by the patterns. So your function mapm has
actually 3 arguments, the 3rd of which is a pattern. I guess you
intended to do some pattern matching on the two arguments of your
function, which would be
let rec mapm func list = match func, list with
| _, [] -> []
| _, head :: tail -> func head :: mapm func tail
but there is no need to do some pattern matching on the function, so
let rec mapm func = function
| [] -> []
| head : :tail -> func head :: mapm func tail
would equally do, which is (regardless of the evaluation order) the
code of List.map that you can find in the ocaml standard library.
I you don't mind a comment: I think there is also a mailing list for
ocaml beginners.
Best regards,
--
Jean-Christophe Filliâtre (http://www.lri.fr/~filliatr)
prev parent reply other threads:[~2005-10-27 13:50 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-10-27 13:30 Alexander A. Vlasov
2005-10-27 13:41 ` [Caml-list] " Luc Maranget
2005-10-27 14:40 ` Damien Doligez
2005-10-27 13:50 ` Jean-Christophe Filliatre [this message]
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