Gambit-list Juillet 2007

gambit-list@iro.umontreal.ca

14 participants
16 discussions

switching threads in the repl?
by Phil Dawes 17 Jul '07

17 Jul '07

Hi Gambit list, Is there a way to switch threads in the repl? I'm running a webserver based on the http.scm example that comes with gambit, and I'd like to be able to switch to an errored thread to get a backtrace and step through it. (or have I mis-understood part of how this all works?) Many thanks, Phil

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Is r6rs ready for try out in gambit-c?
by naruto canada 17 Jul '07

17 Jul '07

hi Is r6rs ready for try out in gambit-c? Thanks

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Prototype Gambit-C Erlang FFI
by James Long 16 Jul '07

16 Jul '07

Hey guys, I don't know if anyone would be interested in this, but I've been playing around with the idea of using Scheme underneath Erlang. I'm very new to both Erlang and Scheme, and I was hoping to be able to seamlessly create Scheme nodes within Erlang. Because of Erlang's own implementation of lightweight processes, it turns out that it can't be as seamless as I had hoped, but I created a Gambit Erlang FFI to see what it would be like anyway. download it here (it only compiles on OS X, but very small tweaks to the makefile could fix that): http://dimlylitblog.com/projects/erlang-ffi.tar.gz To be able to take advantage of all of Erlang's distributing mechanisms, we need to use a proxy Erlang process and communicate through ports, as described here: http://www.erlang.org/doc/tutorial/erl_interface.html#5 This is what my FFI is based on. It's a very basic implementation, but it allows to write a Scheme app like this: (load "erlang") (define (bar num) (+ num 2)) (define (foo num) (* num 2)) (define (start) (start-erl) (let loop ((term (erl-receive))) (if (not (eqv? term 'close)) (begin (let* ((fun (car term)) (args (cdr term)) (res (apply (eval fun) args))) (erl-send (erl-element res)) (loop (erl-receive))))))) (start) And then in Erlang do this: 2> test:start("./test_process"). <0.38.0> 3> test:call({foo,10}). 20 4> test:call({foo,12}). 24 5> test:call({foo,25.2}). 50.4000 6> test:call({foo,12.25}). 24.5000 7> test:call({bar,100}). 102 8> test:call({bar,100.123}). 102.123 9> Unfortunately, it's still not quite as solid as I would like. It communicates over standard in and out, which just seems hacky to me. However, this is my first FFI and it was a good experience. I have a couple questions after writing this though: 1. One of the biggest problems which made development difficult is that if the Scheme node hit any run-time error I cannot see it from Erlang at all. I could catch the exceptions myself and propagate them properly, however there seems to be run-time errors which are syntactual/macro errors, etc. would there be any good methods to detect and this log those kinds of errors? 2. When I compile the Erlang FFI, gcc gives this warning: erlang.c:2530: warning: target of assignment not really an lvalue; this will be a hard error in the future and I think it's talking about assigning the result of a c function to ___result, such as ___result = ERL_TUPLE_SIZE(___CAST(ETERM*,___arg1)); any thoughts on that? 3. On OS X, when compiling the FFI into a loadable library, I give gsc options to pass to the linker to link in the erl_interface libraries. It compiles, but when run it gives the error that any of the Erlang c functions can't be found in the flat namespace. I thought that it might be compiling the library with the two level namespace, so I added -flat_namespace to the linker options but it didn't help. I finally figured out that it needed the option "bundle_loader" to work, and I initially tried -bundle_loader $(gsi), but I have no idea why that made it work. I then tried -bundle_loader /bin/ls and even that worked! I understand the purpose of the bundle_loader option, but this should all be in the flat namespace. Has anyone encountered this? I think those are the only things I didn't really understand :) James

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gsi does not support c-lambda??
by David St-Hilaire 10 Jul '07

10 Jul '07

Hi! I don't understand why, but it seems that my gsi doesn't want to support c-lamda expression any longer. For example: > (define pow2 (c-lambda (int) int "power_of_2")) *** ERROR IN (console)(a)1.14 -- Interpreter does not support ##c-lambda I know that before, I could use them without any problems... I also tried to recompile gambit 4 beta 22 without the option enable-cplusplus with no differences... What is happening? I'm not sure since when c-lambda's stopped working, but it might be after the insallation of snow? Thank you for your help! David

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A newbie's question
by Christian von Essen 09 Jul '07

09 Jul '07

Hi, I'm relative new to scheme and chose gambit because of its performance and its debugger over the other implementations. I'm impressed by both features. Especially the debugger is pretty much unique in the scheme systems till under development. There was on this list a discussion about (a) a module system for gambit and (b) a package distribution facility with packages called "gems". I wanted to ask about the current development status of both. Was the package system abandoned for "snow" system? Has the development of the module system come to a halt? Personally, I think that a gambit specific package distribution system would help gambit's development a lot, as I am not good enough to hack gambit directly, but probably good enough to write a package. I envision something like chicken's eggs, of course. But before such a sytem can become useful, a module system is almost required. I read about gambit's namespaces (why are they not documented, anyway?), and as others have stated, it provides a base on which a module system could be written. Is there any plan to do that? As we all now, the R6RS process is ongoing. Does gambit plan to adopt the standard? If not, could you please shortly explain why? A lot of question, and I hope that someone finds time to answer them. Christian von Essen

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09 Jul '07

Let me remind you that if you wish to vote on the ratification of the R6RS draft, you must register before July 15 (less than a week from now!). The instructions are at http://www.r6rs.org/ratification/ . You have to write a short statement of interest demonstrating your interest in the Scheme language. I strongly urge everyone on this list to register to vote since you are obviously interested in Scheme. Here is the statement of interest that I submitted. ( (email-address "feeley(a)iro.umontreal.ca") (full-name "Marc Feeley") (geographic-location "Montreal, QC, Canada") (affiliation "Universite de Montreal") (public-email-address "feeley at iro.umontreal.ca") (web-page-url "http://www.iro.umontreal.ca/~feeley") (statement-of-interest "As a student I was attracted to Scheme by its simplicity, dynamism and expressiveness. My Master's and PhD theses focused on the efficient implementation of Scheme. Since then I have been involved in programming language research, and Scheme has been my language of choice for exploring the design and implementation of functional programming languages. I have written several papers related to Scheme and have taught Computer Science to many students using Scheme. I am the author of a few implementations of Scheme including Gambit, which is well known for its performance, portability and conformance to the Scheme standard (indeed the only fully conformant Scheme to C compiler). I am a founder of the Workshop on Scheme and Functional Programming and a member of its steering committee. I served on the Scheme standard's editor's committee as editor-in-chief. Scheme has been an integral part of my daily activities over the last 20 years.")) For the record, I intend to vote against the ratification of R6RS. Marc

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Gambit-list Juillet 2007