From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Olivier Dion via General Guile related discussions Newsgroups: gmane.lisp.guile.user Subject: Re: C extensions Date: Sun, 21 Feb 2021 17:41:16 -0500 Message-ID: <87wnv159ir.fsf@clara> References: <87zgzx5s3d.fsf@clara> Reply-To: Olivier Dion Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="12223"; mail-complaints-to="usenet@ciao.gmane.io" Cc: guile-user To: Tim Meehan Original-X-From: guile-user-bounces+guile-user=m.gmane-mx.org@gnu.org Sun Feb 21 23:40:42 2021 Return-path: Envelope-to: guile-user@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lDxP7-00033S-Cj for guile-user@m.gmane-mx.org; Sun, 21 Feb 2021 23:40:41 +0100 Original-Received: from localhost ([::1]:43980 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lDxP6-0004Yz-En for guile-user@m.gmane-mx.org; Sun, 21 Feb 2021 17:40:40 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:34824) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lDxOs-0004Ym-Cn for guile-user@gnu.org; Sun, 21 Feb 2021 17:40:26 -0500 Original-Received: from smtp.polymtl.ca ([132.207.4.11]:60088) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lDxOo-0001v9-P5 for guile-user@gnu.org; Sun, 21 Feb 2021 17:40:25 -0500 Original-Received: from localhost (static-198-54-132-116.cust.tzulo.com [198.54.132.116]) by smtp.polymtl.ca (8.14.7/8.14.7) with ESMTP id 11LMeFZu027965 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sun, 21 Feb 2021 17:40:20 -0500 DKIM-Filter: OpenDKIM Filter v2.11.0 smtp.polymtl.ca 11LMeFZu027965 In-Reply-To: X-Poly-FromMTA: (static-198-54-132-116.cust.tzulo.com [198.54.132.116]) at Sun, 21 Feb 2021 22:40:15 +0000 Received-SPF: pass client-ip=132.207.4.11; envelope-from=olivier.dion@polymtl.ca; helo=smtp.polymtl.ca X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: guile-user@gnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: General Guile related discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guile-user-bounces+guile-user=m.gmane-mx.org@gnu.org Original-Sender: "guile-user" Xref: news.gmane.io gmane.lisp.guile.user:17300 Archived-At: On Sun, 21 Feb 2021, Tim Meehan wrote: > Hello Olivier, thanks! > Those functions helped, and now I know where in the source of Guile to look. > > Is "inexact" the same thing as "floating point number" in Guile-speak? I don't think so. If I remember correctly, exact numbers are numbers that can be represented by a quotient of two integers. In other words, any rational number is an exact number. I might be wrong here. I highly suggest that you read the numerical tower from the Guile's texinfo manual for more informations on that. > > Here is one of the functions in my extension - it returns a lognormal > variate. There are a bunch of things like this that could be added to > "random.c" - but I'm imagining that the only user of stuff like that might > be ... me ... anyhow: > > Right now, it doesn't give really helpful errors when you give it a > negative standard deviation: > scheme@(guile-user)> (random:lognormal 0 -1) > $1 = #f In my example, I returned false because this is how I would approach the problem from a C perspective. i.e., returning an error code. I'm still learning on how to work with Scheme. I guess that if you want something more Pythonic, you would throw an exception. > SCM_DEFINE (scm_random_lognormal, "random:lognormal", 2, 1, 0, > (SCM _mu, SCM _sigma, SCM state), > "Return an inexact real in a Log Normal distribution.\n" > "\n" > "@var{mu} - mean of the underlying normal distribution.\n" > "@var{sigma} - standard deviation of the same.\n" > "Optionally, a random @var{state} can be provided.\n" > "See @code{seed->random-state}.") > #define FUNC_NAME s_scm_random_lognormal > { > if (SCM_UNBNDP (state)) > state = SCM_VARIABLE_REF (scm_var_random_state); > SCM_VALIDATE_RSTATE (1, state); > > if (scm_is_false (scm_positive_p (_sigma))) > return SCM_BOOL_F; // I'd like to return some meaningful error > here ... You can use `scm_throw()` to throw an exception. ---------------------------------------------------------------------- /* * This create a symbol that has static linkage in C. You might want * to declare it globally instead. */ SCM_SYMBOL(lognormal_error_key, "invalid-argument"); if (scm_is_false (scm_positive_p (_sigma))) { scm_throw(lognormal_error_key, scm_list_n(SCM_UNDEFINED)); /* Unreachable path! */ assert(0); } ---------------------------------------------------------------------- Note that throwing an error might be easier to do in Scheme itself: ---------------------------------------------------------------------- (throw 'invalid-argument) ---------------------------------------------------------------------- > > double mu = scm_to_double (_mu); > double sigma = scm_to_double (_sigma); > return scm_from_double (exp (mu + sigma*scm_c_normal01 > (SCM_RSTATE(state)))); > } > #undef FUNC_NAME > > On Sun, Feb 21, 2021 at 9:59 AM Olivier Dion > wrote: > >> On Sat, 20 Feb 2021, Tim Meehan wrote: >> > I'm trying my hand a writing C extensions. >> > I've done this for stuff like Matlab before, and was wondering how you do >> > the usual checking of the arguments that are passed in from Guile. >> > >> > In the manual, 6.13.13.1 "C Support" has a few functions. >> > libguile/numbers.h has a bunch more ... >> > >> > What I have is an extension function, sort of like the bessel function in >> > the tutorial: >> > >> https://www.gnu.org/software/guile/manual/html_node/A-Sample-Guile-Extension.html >> >> Usually I do this in 2 or 3 steps. >> >> 1. Define the primitive in C with raw arguments. >> >> 2. Make a wrapper of this primitive for Guile to use. Optionnaly do >> the arguments checking here or go to step 3. >> >> 3. Make a second wrapper in Scheme and check the arguments there. >> This wrapper will call wrapper in made in 2. >> >> Here's a full example: >> ---------------------------------------------------------------------- >> float c_sin(double x) >> { >> return sin(x); >> } >> >> SCM_DEFINE(c_sin_wrapper, "sin", 1, 0, 0, >> (SCM x), >> "My sine") >> { >> if (scm_is_number(x)) { >> return c_sin(scm_to_double(x)); >> } >> >> return SCM_BOOL_F; >> } >> ---------------------------------------------------------------------- >> >> > What I would like to do is verify that the first argument is an inexact >> > number, larger than 0. How would I go about that? Perhaps some of it >> > could >> >> For your example, use the following predicates: >> ---------------------------------------------------------------------- >> scm_is_inexact(x) && scm_is_true(scm_positive_p(x)) >> ---------------------------------------------------------------------- >> >> > be: >> > SCM_REALP >> > scm_misc_error >> > >> > Any tips? >> -- >> Olivier Dion >> PolyMtl >> -- Olivier Dion PolyMtl