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Writing apps for the iPhone in Scheme
by James Long 18 Jui '09

18 Jui '09

Hey guys, Several people have requested an article about using Gambit Scheme on the iPhone. I finally finished it. You can view it here: http://jlongster.com/blog/2009/06/17/write-apps-iphone-scheme/ Thanks to Marc for editing it a bit. I'm not sure if I can make these kinds of posts too often... it's painstaking! - James

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two threads in the same gambit process; one debugging the other
by lowly coder 17 Jui '09

17 Jui '09

Here's the problem: I have a gambit process P. There are two threads, T1 and T2 running in it. T1 has a gtk window with a textbox open. When T2 throws an exception, instead of debugging T2 at the terminal, I would like to debug T2 in the textbox in T1. Question is -- how do I get T1 to get the repl of T2 when T2 throws an exception? Thanks!

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why's meroon and jazz so special?
by lowly coder 17 Jui '09

17 Jui '09

I was recently looking at mem.c and see that theyre are special constants for object types ... and i saw #define's for meroon and jazz -- why are they so special to be in the C part of Gambit? Thanks! [not complaining, just curious]

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SSL?
by Lam Luu 15 Jui '09

15 Jui '09

Hello all, Do you know if Gambit supports things like SSL for secure connections with clients? Thank you, Lam Luu

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unloading *.o files
by lowly coder 14 Jui '09

14 Jui '09

gsc foo.scm --> foo.o1 my system loads in foo (foo.o1) changes to foo.scm; gsc foo.scm -> foo.o2 when I try to reload foo (foo.o2), it complains that it can't load an object file twice is there some way I can unload foo.o1 ? Thanks!

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Seekable String Ports
by Taylor Venable 13 Jui '09

13 Jui '09

Is there any way to seek through string ports? When I try to use input-port-byte-position I get this: > (call-with-input-string "asdf" (either (char/exactly #\c) (char/exactly #\s))) *** ERROR IN #<procedure #10>, "tcv-gambit-parse.scm"@66.20 -- (Argument 1) Device INPUT PORT expected (input-port-byte-position '#<input-port #11 (string)>) (I'm doubtful that input-port-byte-position would be what I want anyway if the string included characters that weren't encoded as single bytes, but that's a digression.) I'm trying to write a parser combinator library, and part of that entails some rewinding of streams for ordered-choice operations (as illustrated above). A potential alternative would be to duplicate the port's contents and use a different port for each alternative, but I am not aware of any API to do this either. Any ideas on how to accomplish this objective? I need something that works for at least string ports and device ports. My current code, for background: (define char/exactly (lambda (c) (lambda (stream) (let ((char (read-char stream))) (cond ((eof-object? char) #f) ((not (char=? char c)) #f) (else char)))))) (define either (lambda combinators (lambda (stream) (let loop ((c combinators)) (cond ((null? c) #f) ((apply (car c) (list stream)) #t) (else (loop (cdr c)))))))) As defined here, the either function will not undo the changes done by char/exactly (in the example above), thus each choice will advance the stream by one character. We could work around it here by using peek-char rather than read-char but that wouldn't scale to when either is used on functions that read large chunks of data before failing. Thanks for any ideas, -- Taylor Christopher Venable http://real.metasyntax.net:2357/

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define-syntax and loading files
by Taylor Venable 13 Jui '09

13 Jui '09

I'm having some trouble understanding the behavioural differences in this code: BEGIN FILE test-alpha.scm -------------------------------------------- (define-syntax foo (syntax-rules (xyzzy) ((_ xyzzy) "nothing happens"))) BEGIN FILE test-beta.scm --------------------------------------------- (load "test-alpha.scm") (define bar (lambda () (foo hello))) ====================================================================== If I load test-beta.scm twice, I get an error on the second load but not on the first one: > (load "test-beta.scm") "/home/taylor/cvs_public/Programs/Libraries/Scheme/test-beta.scm" > (load "test-beta.scm") *** ERROR IN %%chi-macro437, "/opt/gambit/lib/syntax-case.scm"@9135.1 -- invalid syntax (foo hello) But if I do what seems like it should be the equivalent of loading test-alpha.scm, then loading test-beta.scm I get an error on the first load of test-beta: > (load "test-alpha.scm") "/home/taylor/cvs_public/Programs/Libraries/Scheme/test-alpha.scm" > (load "test-beta.scm") *** ERROR IN %%chi-macro437, "/opt/gambit/lib/syntax-case.scm"@9135.1 -- invalid syntax (foo hello) It seems to me that loading test-beta by itself should be the same as loading test-alpha then test-beta, but it's not quite. Why is this? For what it's worth, my Gambit version string is: v4.4.4 20090611032636 amd64-unknown-openbsd4.5 "./configure --prefix=/opt/gambit --enable-single-host" Thanks, -- Taylor Christopher Venable http://real.metasyntax.net:2357/

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serialization of promises
by Darren Baker 12 Jui '09

12 Jui '09

Marc - Gambit doesn't allow automatic serialization of promises (delay/force) using object->u8vector, is this by design or otherwise? It seems I could get around this by rolling my own force and delay, but perhaps there's a good reason not to be trying to serialize such things? As an aside, I also noticed that there's a ##promise? predicate but no non-## version. Seemed a bit odd. Cheers Darren

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[ANN] Gambit-C v4.4.4 released
by gambit＠iro.umontreal.ca 11 Jui '09

11 Jui '09

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Proposed changes to makefile targets
by Marc Feeley 10 Jui '09

10 Jui '09

Currently the Gambit makefiles support these targets (and more): % make mostlyclean Removes all the files that can be regenerated using standard tools (C compiler, TeX, etc). The C files generated by gsc, and the gsi and gsc executables are not removed. % make clean Removes all the files that can be regenerated by a "make" (object files, C files generated by gsc, etc) **except** gsi and gsc. This is useful to bootstrap from the Scheme sources after gsc has been built with an initial "make bootstrap". % make realclean Like "make clean", but also removes gsi and gsc, and all the makefiles generated by the configure script. This is often confusing for newcomers because in most open-source projects a "make clean" followed by "make" usually restarts the build process from the state of the distributed sources. Currently, the Gambit makefiles will remove all the C files generated by gsc (which are distributed in the tar file), so in fact the system won't build unless the user had successfully done a "make bootstrap". To remove the confusion I'm going to rename the targets as follows: new "clean" target = old "mostlyclean" target new "realclean" target = old "clean" target + old "realclean" target The mostlyclean target will be removed. Moreover, a "make" will be equivalent to a "make bootstrap" unless the gsc-comp (Gambit compiler for bootstrapping) exists. This way, the user can get out of trouble if he does a "make realclean" after a "make". Please let me know if you have suggestions. Marc

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