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FFI
by FFT 22 Mai '09

22 Mai '09

I asked this in comp.lang.scheme already: Is it possible to declare C types that are structs that include arrays (not pointers)? Also, what about bit fields? The answer I got in comp.lang.scheme is that one needs to use lists of strings (?!) for the former. Perhaps I'm missing something, but this seems to be very kludgy, even if it does work. Structs that have arrays are pretty common in C APIs (Bit fields happen too) What's the best approach here?

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define-type with constraints
by lowly coder 22 Mai '09

22 Mai '09

I realize the purpose of define-type is to create structs, but I have struct with some constarints that must be satisfied, like in define-type.scm I want two vars, 'x' and 'twice-x', where twice-x = (* 2 x) In my code, I have created good-x-set! and good-twice-x-set! However, how do I overwrite the existing linked-x-set! and linked-twice-x-set! with my good-x-set! and good-twice-x-set! ? Thanks!

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Vector of Scheme Objects
by lowly coder 22 Mai '09

22 Mai '09

This seems like a really dumb question, and it's probably in the manual, but I can't find it. So I know that I can make a vector of u8s / floats, etc ... but what if I want a vector of scheme objects (and I want the pointer from the vector to the scheme object to be considered a link for the purpose of garbage collection). What do I use for this? I don't want lists since they're O(n), nor maps since they're O(log n), i could use a hashtable ... but I'd prefer to use an array. Thanks!

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Bad version 3.0
by Frank Gizinski 21 Mai '09

21 Mai '09

To Whom it may concern, I mentioned this in an earlier message but I got no answer. I was trying to avoid having my downloads of the newest Versions of Gambit-C held up by Microsoft's security so I downloaded Version 3.0 which worked on my old Macintosh. I downloaded the Microsoft Virtual C++ version from your site and when I got it I started using it. In the first line I typed an opening and closing parenthesis. Instead of those I got an opening and closing angle bracket *<* and *>* . Unless Scheme has recently changed from using parenthesis to angle brackets something seems wrong. Couldn't someone at Montreal check to see what has happened at their site? I doubt that I've got a virus that only effects Gambit-C. I downloaded DrScheme and that works all right. I only checked the parenthesis and the angle brackets, I don't know what else could be wrong with Version 3.0 on your site. Frank Gizinski

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Re: [gambit-list] automatic int -> double conversion
by Marc Feeley 21 Mai '09

21 Mai '09

On 19-May-09, at 4:44 PM, lowly coder wrote: > This is a lot of manual wrapping. Can I define a 'type' like a > lenient-double to have this automatically called? (Then I can sed my > *.scm for double -> lenient-double) Yes you can define your own type with converter functions. The hardest thing to implement is the conversion of bignums and exact rationals to double (the exact->inexact function does this in Scheme). Marc

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Converting (unsigned char *) into u8vector?
by Taylor Venable 20 Mai '09

20 Mai '09

I have some binary data which is stored in an (unsigned char *) and I want to convert it into a u8vector. So I tried writing a conversion function like this: ___SCMOBJ BYTEARRAY_to_SCMOBJ (unsigned char *src, ___SCMOBJ *dst, int arg_num) { unsigned char *srcp = src; unsigned int size; int i = 0; bcopy(src, &size, sizeof(unsigned int)); src += sizeof(unsigned int); ___SCMOBJ ___err = ___FIX(___NO_ERR); ___BEGIN_ALLOC_U8VECTOR(size); for (i = 0; i < size; i += 1) { ___SCMOBJ scm_int; ___err = ___EXT(___U8_to_SCMOBJ) (src[i], &scm_int, arg_num); if (___err != ___FIX(___NO_ERR)) return ___FIX(___UNKNOWN_ERR); ___ADD_U8VECTOR_ELEM(i, scm_int); ___EXT(___release_scmobj) (scm_int); } ___END_ALLOC_U8VECTOR(size); dst = ___GET_U8VECTOR(size); return ___FIX(___NO_ERR); } (This function will be used by macros to support c-define-type. I'm storing the size of the array in the first sizeof(int) bytes, like a "Pascal string" does.) By looking through gambit.h I found some macros which seem to apply to making and manipulating u8vectors, such as ___ADD_U8VECTOR_ELEM. However, they use a variable ___hp which isn't defined anywhere. Is this the right API to use for this sort of thing? Or if not hopefully somebody can share an example of this kind of conversion that I can use as a guide. Thanks, -- Taylor Christopher Venable http://real.metasyntax.net:2357/

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automatic int -> double conversion
by lowly coder 20 Mai '09

20 Mai '09

I have a C/ffi function that expects a double as an argument. If I do (foo 0.0) <-- works fine if I do (foo 0) <-- complains about int / double mismatch; which makes sense. Is there a way to automatically have gambit convert ints to doubles? Thanks!

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Scheme Workshop 2009: deadline NOT extended!
by John Clements 19 Mai '09

19 Mai '09

It's now three weeks until the Scheme Workshop deadline. We won't be extending the deadline, but this should still give you plenty of time to put together your magnificent Scheme Workshop paper. Thanks! John Clements *********************************************** SCHEME AND FUNCTIONAL PROGRAMMING WORKSHOP 2009 Cambridge, Massachusetts August 22, 2009 2ND CALL FOR PAPERS http://www.schemeworkshop.org/2009/ *********************************************** The Scheme and Functional Programming Workshop showcases research and experience related to Scheme, and more broadly to all aspects of functional programming. Areas of interest include: * Language Design, Type Systems, Theory * Program Development Environments, Education * Agile Methodologies, Lightweight Software Engineering * Applications, Implementation, and Experience * SRFIs! In addition to technical papers on matters of programming-language research, we encourage submissions that present experience or innovation with a particular project. The key criterion for any paper--technical or not--is that it makes a contribution from which other practitioners can benefit. ** Dates: ** Dates are firm, and will not be extended. Please plan accordingly. Submission Deadline: June 5, 2009 (FIRM) Author Notification: June 26, 2009 Final Papers Due: July 24, 2009 Workshop: August 22, 2009 ** Program Committee: ** John Clements, Cal Poly State University (organizer & chair) Dominique Boucher, Nu Echo Abdulaziz Ghuloum, Indiana University David Herman, Northeastern University Shriram Krishnamurthi, Brown University Matthew Might, University of Utah David Van Horn, Northeastern University ** Publication Policy: ** Submitted papers must have content that has not previously been published in other conferences or refereed venues, and simultaneous submission to other conferences or refereed venues is unacceptable. Publication of a paper at this workshop is not intended to replace conference or journal publication, and does not preclude re-publication of a more complete or finished version of the paper at some later conference or in a journal. ** Submission Instructions: ** Your submissions should be no longer than 12 pages, including bibliography and appendices. Papers may be shorter than this limit, and the Program Committee encourages authors to submit shorter papers where appropriate. The conference web page (URL above) contains detailed formatting instructions and LaTeX support files. Submit your papers using the Continue 2.0 submission server, at the URL: http://continue2.cs.brown.edu/scheme2009/ We look forward to reading your papers! \

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c-define-type pointer
by lowly coder 18 Mai '09

18 Mai '09

Marc, can you explain how pointer, of (c-define-type ... (pointer ...)) fame works? (and also where i can find it's source / reimplement it myself) Thanks!

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more problems with blackhole
by lowly coder 18 Mai '09

18 Mai '09

In the following code, what I'm trying to understand is ... why does the namespace seem to treat functions and macros separately? In particular, there does not seem to be anyway for me to access 'bar' in test2 once I (export) ~/magic$ cat test.scm (define (foo x) (list x x)) (define-macro (bar x) `(list ,x ,x)) ~/magic$ cat test2.scm (export) (define (foo x) (list x x)) (define-macro (bar x) `(list ,x ,x)) ~/magic$ bsc > (import test) > foo #<procedure #2 test#foo> > bar *** ERROR IN ##main -- Macro name can't be used as a variable: bar > *** EOF again to exit ~/magic$ bsc > (import test2) > foo *** ERROR IN (console)(a)2.1 -- Unbound variable: ~#foo 1> bar *** ERROR IN (console)(a)3.1 -- Unbound variable: ~#bar 2> test2#foo #<procedure #2 test2#foo> 2> test2#bar *** ERROR IN (console)(a)5.1 -- Unbound variable: test2#bar 3> 2> 1> > *** EOF again to exit i realize there are workarounds to this ... but

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