[cwn] Attn: Development Editor, Latest Caml Weekly News

[Alan Schmitt]

Hello,

Here is the latest Caml Weekly News, for the week of October 27 to November
03, 2009.

1) forbidden construct as right hand side of "let rec"
2) ocaml-gettext v0.3.3
3) Other Caml News

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1) forbidden construct as right hand side of "let rec"
Archive: <
http://groups.google.com/group/fa.caml/browse_thread/thread/a6696d235d8843a5#
>
------------------------------------------------------------------------
** Mathias Kende and Lukasz Stafiniak asked, and Xavier Leroy answered:

Mathias Kende wrote:
> I need to write something like this :
>
>       let f f i = if i = 0 then 1 else i * f (i - 1)
>       let rec g = f g
>
> Of course the compiler won't let me write it (even if the OCaml type
> system is happy):
>       "This kind of expression is not allowed as right-hand side of `let
rec'"
In general, the best thing to do in this case is to switch to lazy
evaluation:

# let f f i = if i = 0 then 1 else i * Lazy.force f (i-1);;
val f : (int -> int) Lazy.t -> int -> int = <fun>
# let rec g' = lazy (f g');;
val g' : (int -> int) Lazy.t = <lazy>
# let g = Lazy.force g';;
val g : int -> int = <fun>
# g 10;;
- : int = 3628800

Lukasz Stafiniak wrote:
> While we are at it, what is the best way to convert a "straight" list
> into a cyclic list?
>
> i.e. convert
>
> let l = a::b::[]
>
> into
>
> let rec l = a::b::l
>
> (for arbitrary length lists). (The answer I recall from the archives
> was using Obj.magic to mutate the [] in the original list).

Obj.magic is not part of the OCaml language :-)

Again, you can do that just fine using lazy lists instead of lists:

type 'a lazylist = 'a lazylist_content Lazy.t
and 'a lazylist_content = Nil | Cons of 'a * 'a lazylist
========================================================================
2) ocaml-gettext v0.3.3
Archive: <
http://groups.google.com/group/fa.caml/browse_thread/thread/ee192e030bf1e9b7#
>
------------------------------------------------------------------------
** Sylvain Le Gall announced:

General:
ocaml-gettext is a library that enables string translation in OCaml. The
API is based on GNU gettext. It comes with a tool to extract strings
which need to be translated from OCaml source files.

This enables OCaml program to output string in the native language of
the user, if a corresponding translation file of the English strings is
provided.

Changes:
v 0.3.3 is a bug fix release:
* compatible with ocaml-fileutils 0.4.0
* more static type-check of format string

Links:
<http://le-gall.net/sylvain+violaine/ocaml-gettext.html>
<http://le-gall.net/sylvain+violaine/download/ocaml-gettext-0.3.3.tar.gz>
========================================================================
3) Other Caml News
------------------------------------------------------------------------
** From the ocamlcore planet blog:

Thanks to Alp Mestan, we now include in the Caml Weekly News the links to
the
recent posts from the ocamlcore planet blog at <http://planet.ocamlcore.org/
>.

OCaml-gettext 0.3.3:
  <http://caml.inria.fr/cgi-bin/hump.cgi?contrib=436>

It?s coming:
  <http://dutherenverseauborddelatable.wordpress.com/2009/11/01/its-coming/>

Liquidsoap 0.9.2 is out !:
  <http://blog.rastageeks.org/spip.php?article52>

BlackBerry OS 5.0 and the Storm:
  <
http://feedproxy.google.com/~r/Skydeck/~3/gtTzD9h8p_s/blackberry-os5-storm>

XML or S-expressions?:
  <http://rwmj.wordpress.com/2009/10/30/xml-or-s-expressions/>

ocamlbuild example repository:
  <http://forge.ocamlcore.org/projects/obuild-examples/>

New HLVM GC and LLVM 2.6 support:
  <http://forge.ocamlcore.org/forum/forum.php?forum_id=449>

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