[Caml-list] Ocaml interface to ctype.h functions

[Caml-list] Ocaml interface to ctype.h functions

[Shawn Wagner]

I've been working on some projects recently where it would be nice to have
access to the ctype.h character classification functions (isalpha(),
isspace(), etc.) in Ocaml, and couldn't find anything like them in a search
through the standard library. It's easy to whip up a library for this, but
before doing so, I thought I'd ask if there's any plans to put them in the
Character module or some other place it makes sense to have them. If it's
just a matter of waiting for someone to do it, I'm willing to volunteer, as
I'd probably be doing it anyways on my own.


-- 
Shawn Wagner
shawnw@speakeasy.org
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RE: [Caml-list] Ocaml interface to ctype.h functions

[Michael Hicks]

Perhaps these are things that could/should be added to the Char module?
Mike

> -----Original Message-----
> From: owner-caml-list@pauillac.inria.fr
> [mailto:owner-caml-list@pauillac.inria.fr]On Behalf Of Shawn Wagner
> Sent: Saturday, June 02, 2001 2:25 AM
> To: caml-list@inria.fr
> Subject: [Caml-list] Ocaml interface to ctype.h functions
>
>
> I've been working on some projects recently where it would be nice to have
> access to the ctype.h character classification functions (isalpha(),
> isspace(), etc.) in Ocaml, and couldn't find anything like them
> in a search
> through the standard library. It's easy to whip up a library for this, but
> before doing so, I thought I'd ask if there's any plans to put them in the
> Character module or some other place it makes sense to have them. If it's
> just a matter of waiting for someone to do it, I'm willing to
> volunteer, as
> I'd probably be doing it anyways on my own.
>
>
> --
> Shawn Wagner
> shawnw@speakeasy.org
> -------------------
> To unsubscribe, mail caml-list-request@inria.fr.  Archives:
http://caml.inria.fr

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Re: [Caml-list] Ocaml interface to ctype.h functions

[Shawn Wagner]

On Sat, Jun 02, 2001 at 09:25:16AM -0400, Michael Hicks wrote:
> Perhaps these are things that could/should be added to the Char module?
> Mike

Yeah. Not sure why I said Character when I really meant Char. 


-- 
Shawn Wagner
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Re: [Caml-list] Ocaml interface to ctype.h functions

[Luc MAZARDO]

You can see at :
http://www.ocaml.org/bin/caml-bugs/feature%20wish?id=57;user=guest#followups

Actually, Char.{upper,lowercase} seems to work only for ASCII systems. :(

Friendly.
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Re: [Caml-list] Ocaml interface to ctype.h functions

[Shawn Wagner]

On Tue, Jun 05, 2001 at 09:35:58AM +0200, Luc MAZARDO wrote:
> 
> You can see at :
> http://www.ocaml.org/bin/caml-bugs/feature%20wish?id=57;user=guest#followups
>

Hmm. Too bad that's over a year old, still not in the distribution (At
least, not the relevant bits), and works only with ascii and English. At
least now I know where to send the patch when I find the time to actually do
it... hopefully sometime this week.

> Actually, Char.{upper,lowercase} seems to work only for ASCII systems. :(
> 

I'll probably re-do them to use the C toupper()/tolower() functions. Might
have to add Sys.set_locale as well while I'm at it.

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Re: [Caml-list] Ocaml interface to ctype.h functions

[Xavier Leroy]

> I've been working on some projects recently where it would be nice to have
> access to the ctype.h character classification functions (isalpha(),
> isspace(), etc.) in Ocaml, and couldn't find anything like them in a search
> through the standard library. It's easy to whip up a library for this, but
> before doing so, I thought I'd ask if there's any plans to put them in the
> Character module or some other place it makes sense to have them.

It would make sense to have classification functions in the Char
module.  The main issue is: what is a letter?, or: how to deal with
character sets.

If only one, fixed character set is supported (e.g. US-ASCII or
Latin-1), it's truly easy, but will not satisfy everyone.  OCaml has
already been criticized for supporting ISO Latin-1 accented letters in
identifiers!  (Look at the caml-list archives if you don't believe me.)

Building on the C functions isalpha(), etc, is a bit of a cop-out,
because then we're dependent on what these functions actually do on a
variety of Unix, Windows and Macintosh systems.  In particular, we
become dependent on the ISO C internationalization framework ("locales"),
which I think is a mess because it relies too much on a global state
(the current locale).

To give an example of the kind of problems I fear, just doing
setlocale(LC_ALL, "fr_FR") in an OCaml program causes
float_of_string "3.14" to return 0.0.  Guess why?  float_of_string
relies on the C function atof(), which is internationalized, and
doesn't recognize "." as a decimal point -- French uses a "," instead...

Finally, there's the Unicode approach.  Letters, etc, are well defined
without reference to a "locale" or whatever piece of state.  But then
we've just shifted the problem to a more general one: retrofitting
Unicode into OCaml, which again has been the subject of lively
discussions on this mailing list :-)

> If it's
> just a matter of waiting for someone to do it, I'm willing to volunteer, as
> I'd probably be doing it anyways on my own.

It's mostly a matter of knowing what we want these classification
functions to do.  Meanwhile, it might be easier to define your own
isalpha, etc, predicates; at least you get to choose the encoding!
Besides, it's really easy using pattern-matching, e.g. for ASCII:

let isalpha = function 'A'..'Z'|'a'..'z' -> true | _ -> false

- Xavier Leroy
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Re: [Caml-list] Ocaml interface to ctype.h functions

[Sylvain Kerjean]

Xavier Leroy wrote:
> 
> It's mostly a matter of knowing what we want these classification
> functions to do.  Meanwhile, it might be easier to define your own
> isalpha, etc, predicates; at least you get to choose the encoding!
> Besides, it's really easy using pattern-matching, e.g. for ASCII:
> 
> let isalpha = function 'A'..'Z'|'a'..'z' -> true | _ -> false
>

I did it at the compiler level, shortcutting (is it english ??) the call
to  the C isalpha function
in the lexer and coded my own in order to support accented letters in my
compiler (it worked bad on BeOS). But i realize i coudln't share my
programs anymore with an unmodified compiler :/

So I think it is a good idea to have standard characters let's say
simple ascii and let users
re-implement an isalpha() predicate at the user level ...
And if there are some good unicode coders here, i am greatfully
interested !


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Sylvain Kerjean
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Re: [Caml-list] Ocaml interface to ctype.h functions

[Chris Hecker]

>It's mostly a matter of knowing what we want these classification
>functions to do.  Meanwhile, it might be easier to define your own
>isalpha, etc, predicates; at least you get to choose the encoding!
>Besides, it's really easy using pattern-matching, e.g. for ASCII:

But, we've got someone willing to do the work for everybody, so it seems a shame not to use it just because we can't figure out what the 100% Right Thing is.  

How about putting a nested ASCII (or ISO_Latin_1, or whatever) module inside Char, and putting the ascii specific functions in there?  That way it's clear what they're doing and what they support, and we still get to use the fruits of his free labor.  ;)

And then you can add a Unicode one, when we find somebody to do that, etc.

Chris


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Re: [Caml-list] Ocaml interface to ctype.h functions

[Shawn Wagner]

On Tue, Jun 05, 2001 at 06:29:09PM +0200, Xavier Leroy wrote:
> > I've been working on some projects recently where it would be nice to have
> > access to the ctype.h character classification functions (isalpha(),
> > isspace(), etc.) in Ocaml, and couldn't find anything like them in a search
> > through the standard library. It's easy to whip up a library for this, but
> > before doing so, I thought I'd ask if there's any plans to put them in the
> > Character module or some other place it makes sense to have them.
> 
> It would make sense to have classification functions in the Char
> module.  The main issue is: what is a letter?, or: how to deal with
> character sets.
> 
> If only one, fixed character set is supported (e.g. US-ASCII or
> Latin-1), it's truly easy, but will not satisfy everyone.  OCaml has
> already been criticized for supporting ISO Latin-1 accented letters in
> identifiers!  (Look at the caml-list archives if you don't believe me.)
> 
> Building on the C functions isalpha(), etc, is a bit of a cop-out,
> because then we're dependent on what these functions actually do on a
> variety of Unix, Windows and Macintosh systems.  In particular, we
> become dependent on the ISO C internationalization framework ("locales"),
> which I think is a mess because it relies too much on a global state
> (the current locale).

Okay, I've done the isFOO() and setlocale() interface as a seperate library
for now, and will release it soon (Like, tonight). Am I correct in assuming
that it's not likely to make it into the standard library based on the
above, though?

I've discovered that setlocale() of LC_CTYPE is done already by the runtime,
by a function used in Char.escaped... so if locales are a mess, they're a
mess ocaml is already stuck with.  Also, someone else is asking about a way
to set LC_NUMERIC from in ocaml, so I'm not alone in having a need for
setlocale, at least.


> 
> To give an example of the kind of problems I fear, just doing
> setlocale(LC_ALL, "fr_FR") in an OCaml program causes
> float_of_string "3.14" to return 0.0.  Guess why?  float_of_string
> relies on the C function atof(), which is internationalized, and
> doesn't recognize "." as a decimal point -- French uses a "," instead...

This is why LC_ALL is bad, and why it's better to just use the specific
locale categories you want.


-- 
Shawn Wagner
shawnw@speakeasy.org
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