Mars 2009 - Gambit-list - mailman.iro.umontreal.ca

Why MIT switched from Scheme to Python
by Bradley Lucier 26 Mar '09

26 Mar '09

The original content is from another blog, but this excerpt is of particular interest ... Brad http://www.wisdomandwonder.com/link/2110/why-mit-switched-from-scheme- to-python

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REPL via TCP/IP
by vasil 24 Mar '09

24 Mar '09

Last day I wrote simple remote REPL functionality. It may be useful for someone, who like to work with gambit on remote basis. See attachment for details. Vasil.

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redefine macro variable
by Eduardo Cavazos 23 Mar '09

23 Mar '09

Sorry if this is an FAQ... Is there any way around this: > (define time 0) *** ERROR IN (console)(a)1.9 -- Macro name can't be used as a variable: time > Section 6.3 of the manual documents 'define-macro' but it doesn't go into this. Ed

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passing an f64vector
by Eduardo Cavazos 23 Mar '09

23 Mar '09

Hello, The type of the second parameter of gl function glGetDoublev is GLdouble*. So, I'd like to be able to pass an f64vector as that argument. The declaration of glGetDoublev is: void glGetDoublev( GLenum pname, GLdouble *params ) So something along these lines I guess: (define glGetDoublev (c-lambda (GLenum scheme-object) void " glGetDoublev ( ___arg1 , UNPACKTHEVEC( ___arg2 ) ) ; ")) Except with the proper unpacking of ___arg2. Any suggestions as to what macro to use there? I'm looking through gambit.h... Ed

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gambit introspection
by Jose A. Ortega Ruiz 22 Mar '09

22 Mar '09

hi, i'm working in a scheme-emacs interaction environment providing a subset of the capabilities present in slime. although i'm using guile as the initially supported scheme, the framework is generic on the emacs side and it shouldn't be difficult to add support for other schemes. i'd like to add gambit to the party, but i'm having a hard time finding procedures to obtain metadata about objects living in a running interpreter instance. so far, i've only found ##procedure-locat. in addition, it'd be nice to have: - general location info (the equivalent of ##procedure-locat for macros and variables) - a way of getting all defined bindings starting with a prefix (gsi's REPL does this, but i haven't found how) - a way of getting the arity and parameter names for procedures and macros - a way of getting a procedure's callers and callees - macroexpand: i see there's a family of ##macro-* procedures, but i'm not sure how to use them - metadata associated with namespaces - any other metadata associated with objects that could be used in an inspector although i haven't had the time, i'm sure gambit.el will give me enough clues to interact with the debugger. documentation-wise, my framework knows how to use info docs, so, as long as there're no plans to phase out texinfo as one of gambit's documentation formats, i'm ok on that front too. my apologies if this information is already available somewhere: i'll appreciate it if you send me RTFM with accompanying pointers. thanks a lot for your time. cheers, jao

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current-object-file
by Eduardo Cavazos 22 Mar '09

22 Mar '09

Hello, This is the procedure I'm using to find the current object file for a given scheme file. (define (current-object-file scheme-file) (let ((object-file? (let ((object-file-prefix (string-append (path-strip-directory (path-strip-extension scheme-file)) ".o"))) (lambda (file) (string-prefix? object-file-prefix file))))) (let ((object-files (sort-list (filter object-file? (directory-files (path-directory scheme-file))) string>))) (if (null? object-files) #f (first object-files))))) Comments welcome. Ed

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Can't load a given object file more than once
by Eduardo Cavazos 22 Mar '09

22 Mar '09

Hello, This is not actually that big a deal. But, let's say I compile a file: > (compile-file "/tmp/test-gambit-compiler/test-a.scm") #t Then load the resulting object file: > (load "/tmp/test-gambit-compiler/test-a") "/tmp/test-gambit-compiler/test-a.o1" OK, I wanna recompile it, but not have a bunch of old versions laying around. So delete the o1 file: > (delete-file "/tmp/test-gambit-compiler/test-a.o1") And recompile: > (compile-file "/tmp/test-gambit-compiler/test-a.scm") #t An error occurs if you try to load the new object file: > (load "/tmp/test-gambit-compiler/test-a") *** ERROR IN (console)(a)5.1 -- Can't load a given object file more than once (load "/tmp/test-gambit-compiler/test-a") 1> Sure, I understand that Gambit is preventing a reload of the exact same object file. But it must be doing a very simple accounting based on the name of the object file. Perhaps you can employ that newfangled high-performance file digest code that was recently shared. ;-) Anywho, no big deal. But it's a surprise. Ed

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smart-load
by Eduardo Cavazos 22 Mar '09

22 Mar '09

Hello, Here's fun hack that's a replacement for 'load'. I use something like this with Chicken. If the scheme file doesn't have a corresponding object file or if the object file is out of date, the scheme file is compiled and loaded. Otherwise the object file is loaded. (define (smart-load scheme-file) (let ((object-file (current-object-file scheme-file))) (cond ((and object-file (file-newer? object-file scheme-file) (not (member object-file *gambit-loaded-files*))) (set! *gambit-loaded-files* (cons object-file *gambit-loaded-files*)) (gambit-scheme-load object-file)) ((and object-file (file-newer? object-file scheme-file)) 'already-loaded) (else (print "Compiling file: " scheme-file "\n") (compile-file scheme-file) (smart-load scheme-file))))) Where the supporting procedures are: (define (file-newer? a b) (> (time->seconds (file-info-last-modification-time (file-info a))) (time->seconds (file-info-last-modification-time (file-info b))))) (define (current-object-file scheme-file) (let ((object-file? (let ((object-file-prefix (string-append (path-strip-directory (path-strip-extension scheme-file)) ".o"))) (lambda (file) (string-prefix? object-file-prefix file))))) (let ((object-files (sort-list (filter object-file? (directory-files (path-directory scheme-file))) string>))) (if (null? object-files) #f (string-append (path-directory scheme-file) (first object-files)))))) Ed

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glut callbacks
by Eduardo Cavazos 21 Mar '09

21 Mar '09

Hello, I was trying out the opengl library from the wiki. Some of the functions in the glut library are used to specify callbacks. For example, glutReshapeFunc. In the glut libraries of Ypsilon, Larceny, and Chicken, I'm able to pass a Scheme procedure to the 'glutReshapeFunc' procedure. Is this doable with Gambit? From the sound of the manual, it seems like this is not yet supported. Ed

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Web applications in Gambit
by Andrew Whaley 20 Mar '09

20 Mar '09

Hi Marc, Thanks for your email in response to my post on comp.lang.scheme. For the benefit of the other subscribers, I'm trying to create a web application framework using Gambit that is secure, performant and above all allows great developer productivity. I'm aiming for something similar to SISCWeb but a lot faster and able to support very many concurrent users. I already use Gambit for other things like my win-control library that I use for automated application testing so I really like Gambit. I've made some good progress in the last couple of days by finding the ssax-sxml library and Francisco Ferreira's basic scgi interface. Putting these together with a multithreaded dispatcher, I now have gambit serving complex SXML web pages in around 50ms which is about 20 times faster than SISCWeb with the same page. I have an immediate problem in that the main thread which listens for incoming connections and then spawns handler threads for each page requests works fine if I run it in the REPL window but that then prevents REPL from doing anything else. If I try and spawn a separate thread for this listener so that I can carry on using REPL then the listener stops running unless I repeatedly press return in the REPL window ! I want to keep REPL running concurrently with the listener so that I can redefine procedures on the fly during development rather than having to stop and start gsi and therefore losing any application state. Have I missed something here as it seems that threads are blocked whilst REPL is waiting for input ? I'm using 4.4.0 MinGW Windows version. I have enough working now to start on the continuations based web framework but pretty soon I'll need to try and interface with a backend database e.g. Oracle or MySQL. The obvious way to do this will be to use the relevant C API for the database but I'm guessing that if I call into C then all the pseudo-threads in Gambit will stop until the C call returns - is this correct ? This would probably OK for a short call but would be disastrous for a long running call e.g. to a database that has a latency of at least 30ms and could be several seconds for some queries. Do you have any thoughts on how I could do this ? Many thanks Andrew

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