[Caml-list] Printf and i18n

[Caml-list] Printf and i18n

[Jérôme Marant]

Hi,

  I was thinking about writing a small gettext-like module
  for handling internationalisation of strings in OCaml programs.
  
  But it is quite useless if it cannot work with printf: the
  printf format parameter looks like a string but it isn't
  (printf is using some internal magics).

  Any idea about how this could be handled? Thanks.

  Regards, 

-- 
Jérôme Marant <jerome@marant.org>
              <jerome.marant@free.fr>

http://marant.org
              
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[Caml-list] Modular subject-observer pattern ?

[Pascal Grossé]

Hi,

I'm read how to implement the subject-observer pattern using objects, as
shown on:

http://pauillac.inria.fr/~remy/cours/appsem/ocaml-objects.html#toc13

I have a question : is it possible to have a simple version of this
pattern without using objects, i.e. with modules/functors ?

Thanks,

Pascal Grosse
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Re: [Caml-list] Printf and i18n

[Daniel de Rauglaudre]

Hi,

On Wed, Apr 17, 2002 at 07:37:19PM +0200, Jérôme Marant wrote:

>   I was thinking about writing a small gettext-like module
>   for handling internationalisation of strings in OCaml programs.
>   
>   But it is quite useless if it cannot work with printf: the
>   printf format parameter looks like a string but it isn't
>   (printf is using some internal magics).

In my program GeneWeb, I use internationalization with printf. I have
a function ftransl function defined like this (revised syntax):

  value ftransl lang (fmt : format 'a 'b 'c) : format 'a 'b 'c =
     valid_format fmt (transl lang (Obj.magic fmt : string));

The function "transl", called inside this function, takes the language
and the format fmt constrained to be a string and applies the translation.

The function "valid_format" checks that this resulting translation
has the same % defined in the same order than fmt. Return the translated
format if ok. If not ok, it returns the initial format, but you can
fail, if you prefer.

Therefore, instead of
      printf "hello, my name is %s\n" name
you can write:
      printf (ftransl "hello, y name is %s\n") name

For the translations, I use a lexicon file, containing a list of entries
which I want to be i18n. It is an idea I took from Caml Light. The first
string, without language, is the format to be translated, in a vehicular
language (actually English), and I give the translation in each language
I want. E.g. an entry can be:

     hello, my name is %s\n
 en: hello, my name is %s\n
 es: buenos dias, me llamo %s\n
 fr: bonjour, je m'appelle %s\n

-- 
Daniel de RAUGLAUDRE
daniel.de_rauglaudre@inria.fr
http://cristal.inria.fr/~ddr/
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Re: [Caml-list] Printf and i18n

[John Prevost]

>>>>> "dr" == Daniel de Rauglaudre <daniel.de_rauglaudre@inria.fr> writes:

    dr> For the translations, I use a lexicon file, containing a list
    dr> of entries which I want to be i18n. It is an idea I took from
    dr> Caml Light. The first string, without language, is the format
    dr> to be translated, in a vehicular language (actually English),
    dr> and I give the translation in each language I want. E.g. an
    dr> entry can be:

    dr>      hello, my name is %s\n
    dr>  en: hello, my name is %s\n
    dr>  es: buenos dias, me llamo %s\n
    dr>  fr: bonjour, je m'appelle %s\n

A good try, but unfortunately it doesn't allow for the more
significant problem, which is word order variation.  Imagine a simple
format like:

Printf.printf "%s's %s" "John" "document"

The problem here is that we have the following translations (sort of,
no character sets here):

en: X's Y
ja: X no Y
ru: Y u X

And of course, with more arguments you get more variety.

One solution is to treat your formats as functions, rather than
formats.  This cuts down on the utility somewhat, since you have to
sprintf instead of printing directly, but:

let owns = [En, fun owner owned -> Printf.sprintf "%s's %s" owner owned;
            Ja, fun owner owned -> Printf.sprintf "%s no %s" owner owned;
            Ru, fun owner owned -> Printf.sprintf "%s u %s" owned owner]

sort of gets you moving in the right direction.  Of course, you need
an automated system to handle things reasonably.

This is why many modern printf-style systems, especially those for
handling internationalization, include numbered or named slots to be
filled in.  For example, in Python:

fmt = "%(owner)s's %(owned)s"
fmt = "%(owner)s no %(owned)s"
fmt = "%(owned) u %(owner)"

can all be used as:

fmt % {'owner':'John', 'owned':'document'}

In Java:

fmt = new MessageFormat("{0}''s {1}");
fmt = new MessageFormat("{0} no {1}");
fmt = new MessageFormat("{1} u {0}");

can all be used as:

fmt.format(new Object[] {"John", "document"})

Either of these mechanisms allow reading a format from a catalog and
using it in that way.  The only way I can see doing this with
something like O'Caml's current mechanism is introducing a new format
function like printf which takes a format like:

("%s%s:{0}'s {1}" : ('a,'b,'c) format)
("%s%s:{0} no {1}" : ('a,'b,'c) format)
("%s%s:{1} u {0}" : ('a,'b,'c) format)

Use the % model up front to indicate the argument types in argument
order, then indicate what order the arguments are to be used
separately.  This is, of course, rather ugly.  A richer format
language would be preferable.  If keyword arguments can't be made to
work right when included in the type (as seems likely), perhaps a
format language like Python's, but using numbered argument positions
instead of names, so:

("%s %d" : (string -> int -> 'a,'b,'a) format)

but also

("%(1)d %(0)s" : (string -> int -> 'a, 'b, 'a) format)


John.
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Re: [Caml-list] Printf and i18n

[Jérôme Marant]

On Thu, Apr 18, 2002 at 08:47:53AM +0200, Daniel de Rauglaudre wrote:
> 
> In my program GeneWeb, I use internationalization with printf. I have
> a function ftransl function defined like this (revised syntax):
> 
>   value ftransl lang (fmt : format 'a 'b 'c) : format 'a 'b 'c =
>      valid_format fmt (transl lang (Obj.magic fmt : string));
> 
> The function "transl", called inside this function, takes the language
> and the format fmt constrained to be a string and applies the translation.
> 
> The function "valid_format" checks that this resulting translation
> has the same % defined in the same order than fmt. Return the translated
> format if ok. If not ok, it returns the initial format, but you can
> fail, if you prefer.
> 
> Therefore, instead of
>       printf "hello, my name is %s\n" name
> you can write:
>       printf (ftransl "hello, y name is %s\n") name

  Thanks. That sounds what I'm looking for.

  By the way, in order to improve the localization process, we would need
  to add the "argument reordering" feature to printf functions.
  For instance, with: 

  printf " %2$d %1$s" "foo" 1

  you get : 1 foo

  because some languages do not order words the same way.

  One more question : could you (or any other OCaml developer) give some
  explainations about the Obj module since, even "not for the casual user",
  it can be usefull sometimes (well at least for you and in the printf
  functions)?

  Thanks in advance.

-- 
Jérôme Marant
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Re: [Caml-list] Printf and i18n

[Jacques Garrigue]

>   One more question : could you (or any other OCaml developer) give some
>   explainations about the Obj module since, even "not for the casual user",
>   it can be usefull sometimes (well at least for you and in the printf
>   functions)?

The Obj module lets you access the internal representation of ocaml
objects, as desribed in the "Interfacing with C" section of the
manual.
Once you have understood the details of this representation, you can
start using it sparingly, to avoid having to write external C
functions. i.e. it is best seen as an alternative to writing C code,
and is not much safer than that (just a bit easier at the GC level).

Jacques
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Re: [Caml-list] Printf and i18n

[Chris Hecker]

>The Obj module lets you access the internal representation of ocaml
>objects, as desribed in the "Interfacing with C" section of the
>manual.

It might be useful to explain the printf format string hackery in the 
manual.  It's the only "legitimate" use of Obj.magic;  you have to use it 
if you want to do varargs style functions like printf and parse the 
strings.  Or, is there another use of it in the standard library that I'm 
missing?

Chris


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Re: [Caml-list] Printf and i18n

[Jérôme Marant]

On Thu, Apr 18, 2002 at 05:13:38PM +0900, Jacques Garrigue wrote:
> >   One more question : could you (or any other OCaml developer) give some
> >   explainations about the Obj module since, even "not for the casual user",
> >   it can be usefull sometimes (well at least for you and in the printf
> >   functions)?
> 
> The Obj module lets you access the internal representation of ocaml
> objects, as desribed in the "Interfacing with C" section of the
> manual.
> Once you have understood the details of this representation, you can
> start using it sparingly, to avoid having to write external C
> functions. i.e. it is best seen as an alternative to writing C code,
> and is not much safer than that (just a bit easier at the GC level).

  Alright. Thanks a lot.

-- 
Jérôme Marant
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Re: [Caml-list] Printf and i18n

[Daniel de Rauglaudre]

Hi,

On Thu, Apr 18, 2002 at 10:02:42AM +0200, Jérôme Marant wrote:

>   By the way, in order to improve the localization process, we would need
>   to add the "argument reordering" feature to printf functions.
>   For instance, with: 
> 
>   printf " %2$d %1$s" "foo" 1

I have something like that, indeed. It is also John Prevost's remark.
For that I use the same system of lexicon, but I don't use printf, but
just print_string for this kind of phrases.

I have specific functions to translate that sort of cases. The string
is scanned by an automat to build the resulting string.

I have as example in my lexicon:

       %1 of %2
   cs: %1 :g:%2
   de: %1 von :d:%2
   en: %2's %1
   fr: %1 d[e']%2
   it: %1 d[i']%2
   pl: %1 :g:%2

There is also some system for elision (before vowels), in French and
in Italian. In French, to translate "Adam's car", you have "la voiture
d'Adam", not "la voiture de Adam".

And there is a system of declination in German and Polish. The :g:
introduces the genitive case for the next phrase. And I have a system
to indicate genitive cases for the other terms.

Another case, the way dates are printed:

       (date)
   cs: 1. %m %y/%d. %m %y/%m %y/%y
   de: 1. %m %y/%d. %m %y/%m %y/%y
   en: 1 %m %y/%d %m %y/%m %y/%y
   fr: 1er %m %y/%d %m %y/%m %y/%y
   it: 1o %m %y/%d %m %y/%m %y/%y
   pl: 1 %m %y/%d %m %y/%m %y/%y

%m = month, %y = year %d = day

The slash separate the cases:
   first in the month
   other in the month
   date when there is only month and year
   date when there is only year

Of course, in all these examples, printf does not work: you have to
apply print_string, or printf "%s"

-- 
Daniel de RAUGLAUDRE
daniel.de_rauglaudre@inria.fr
http://cristal.inria.fr/~ddr/
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Re: [Caml-list] Printf and i18n

[Jérôme Marant]

On Thu, Apr 18, 2002 at 10:27:34AM +0200, Daniel de Rauglaudre wrote:
> Hi,
> 
> On Thu, Apr 18, 2002 at 10:02:42AM +0200, Jérôme Marant wrote:
> 
> >   By the way, in order to improve the localization process, we would need
> >   to add the "argument reordering" feature to printf functions.
> >   For instance, with: 
> > 
> >   printf " %2$d %1$s" "foo" 1
> 
> I have something like that, indeed. It is also John Prevost's remark.
> For that I use the same system of lexicon, but I don't use printf, but
> just print_string for this kind of phrases.

  So, if I understood correctly, the string parameters are nothing but
  strings, right?

...

> Of course, in all these examples, printf does not work: you have to
> apply print_string, or printf "%s"

  I'ld love to see the feature in printf though.

  Regards,

-- 
Jérôme Marant
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Re: [Caml-list] Printf and i18n

[Daniel de Rauglaudre]

Hi,

On Thu, Apr 18, 2002 at 11:33:23AM +0200, Jérôme Marant wrote:

> So, if I understood correctly, the string parameters are nothing but
> strings, right?

In this case, yes: I use my own automat instead of (the one of) printf.

> > Of course, in all these examples, printf does not work: you have to
> > apply print_string, or printf "%s"
> 
>   I'ld love to see the feature in printf though.

Could be an idea, indeed.

-- 
Daniel de RAUGLAUDRE
daniel.de_rauglaudre@inria.fr
http://cristal.inria.fr/~ddr/
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