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Is there a way to return "nothing"?
by dillo gimp 01 Mai '07

01 Mai '07

hi Is there a way to return "nothing"? so that : (list nothing 1 2 3 nothing 4 5 6) ; => (1 2 3 4 5 6) I asked the same question on "comp.lang.scheme", but someone says it can't be done. Is this true? ;; (list (if (> 1 2) 3) (if (> 1 2) 3 nil)) ; -> (#!void ()) both "void" and '() are not exactly the same as "absolutely nothing". It would helps a lot if I can code something like that. Thanks.

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GUIDE, and changing REPL/reader interface
by Derek Peschel 30 Avr '07

30 Avr '07

Hi everybody. I'll ask the easy question first: Has anyone compiled GUIDE on any OS lately? On Mac OS 10.3 specifically? (The screenshot I've seen is from Mac OS X, which is a good sign.) I'm trying to get it to compile, I've been running into errors, and it would be nice to know if I have a lot of work ahead of me or not. If it's useful, I can post the errors. But I was trying to use Qt 4 and I didn't configure Gambit with --enable-guide. Now I've reconfigured Gambit and am installing Qt 3, so I'll probably have more relevant errors soon. What I really want is a REPL, or editor interface, that knows about Scheme so it can do parenthesis balancing and symbol lookup, and also talks with the reader so it can edit any line in a multiline S-exp currently being read, mark how much of an input line has been read if it contains more than one S-exp, put whole S-exps in the history instead of lines, and similar things. Emacs has some steps in the right direction -- Taylor Campbell's paredit.el and SLIME being two big ones -- but there are things about Emacs I really don't like. And the usual dumb line-based one-way editor-to-LISP interface won't work very well anyway. SLIME isn't dumb, but it's complicated and I haven't seen documentation of Swank as a protocol. Most other Emacs libraries seem to be based on comint, so I'd call them dumb. The solutions seem to be either fancy streams like CLIM's, or changing the interface between the reader and the editor, perhaps using continuations to implement coroutines. The reader needs the usual "process new input" entry point, but the editor must call the reader and not vice versa. Also, the reader needs another "cancel read in progress" (or maybe "cancel read in progress and process new input") entry point. Is there any documentation about the current implementation of the TTY interface, or the GUIDE variant of the same thing? Is Gambit's abstract stream definition flexible enough to be extended to do what I want? Or does anyone have any examples of combined Scheme/C code that uses continuations? With Scheme's first-class continuations, and Gambit's ease of mixing Scheme and C code (or so I hear), I'm leaning toward the continuation solution. Thanks, -- Derek

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Re: [gambit-list] Big number Bug?
by Bradley Lucier 28 Avr '07

28 Avr '07

I hope you don' t mind me CC'ing my reply to th list. On Apr 25, 2007, at 9:05 PM, dillo gimp wrote: > > > On 4/26/07, Bradley Lucier <lucier(a)math.purdue.edu> wrote: > On Apr 25, 2007, at 7:43 PM, dillo gimp wrote: > > > There might be a bug in big number handling, > > the same code runs fine under mzscheme and petite, but crashes with > > gambit : > > *** ERROR IN ##ratnum.* -- Divide by zero > > (quotient 0 0) > > > > I don't even use "quotient" in my code. > > We'd need to see a bit of your code to figure out what you *are* > using. > > > I don't know how to make gambit to report exactly where the code > has crashed. > The program is not exactly small either. > Can you tell me how to make gambit report "crash point"? > This is my compilation steps: > > cat /lfs/script/gambit.sh > #!/bin/bash > /usr/4.0b22/bin/gsc -prelude '(define (display x) (write x (current- > output-port)))' -link $1 > prog=${1%.sc} > gcc -O2 -fomit-frame-pointer -freg-struct-return \ > -I/usr/4.0b22/include -L/usr/4.0b22/lib \ > -D___SINGLE_HOST -o $prog $prog.c ${prog}_.c -lgambc -lm -ldl - > lutil OK, well I still don't know what you're trying to do, but gambit requires gcc to use certain flags for to correctly compile gambit- generated code. See the options in /usr/4.0b22/bin/

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anyone has a good way for dealing with script clean up?
by dillo gimp 28 Avr '07

28 Avr '07

hi anyone has a good way for dealing with script clean up? I'm mostly writing programs in interpreted mode, ie, with a lot of redundant defines. when I try to compile an interpreted program (assuming it's entirely correct), the only problem while compiling with gsc is the redundant defines. is there a script that can automatically rewrite a program so that it can be compiled to produce the same result as interpreted. Is there deeper issues besides renaming? Thanks.

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define-macro bug?
by dillo gimp 27 Avr '07

27 Avr '07

Ok, this is going to be a bit long: (The same code works for petite and mzscheme.) (The same code cause error in gsi and gsc compiled code.) # cat top.sc (define (top) ( (lambda (input) (cond ((equal? input ''done) (display 'Goodbye) (newline)) (else (display (eval input))(newline) (top) )) ) (read) )) (display "Welcome to toy scheme")(newline) (top) # compile top.sc -> ./top cat bug.sc | ./top .... *** ERROR IN solve-confs-248 -- (Argument 2) REAL expected (> #!unbound 1) cat bug.sc | /usr/4.0b22/bin/gsi top.sc .... *** ERROR IN solve-confs-248 -- (Argument 2) REAL expected (> #!unbound 1) cat bug.sc ;; -------------------------------------------------------------- ;; http://www.ccs.neu.edu/home/dorai/t-y-scheme/t-y-scheme-Z-H-1.html ;; (define amb-fail '*) (define initialize-amb-fail (lambda () (set! amb-fail (lambda () (error "amb tree exhausted"))))) (define-macro amb (lambda alts... `(let ((+prev-amb-fail amb-fail)) (call/cc (lambda (+sk) ,@(map (lambda (alt) `(call/cc (lambda (+fk) (set! amb-fail (lambda () (set! amb-fail +prev-amb-fail) (+fk 'fail))) (+sk ,alt)))) alts...) (+prev-amb-fail)))))) (define number-between (lambda (lo hi) (let loop ((i lo)) (if (> i hi) (amb) (amb i (loop (+ i 1))))))) (define assert (lambda (pred) (if (not pred) (amb)))) (define-macro bag-of (lambda (e) `(let ((+prev-amb-fail amb-fail) (+results '())) (if (call/cc (lambda (+k) (set! amb-fail (lambda () (+k #f))) (let ((+v ,e)) (set! +results (cons +v +results)) (+k #t)))) (amb-fail)) (set! amb-fail +prev-amb-fail) (reverse! +results)))) (define (nreverse rev-it) (cond ((null? rev-it) rev-it) ((not (list? rev-it)) (error "nreverse: Not a list in arg1" rev-it)) (else (do ((reved '() rev-it) (rev-cdr (cdr rev-it) (cdr rev-cdr)) (rev-it rev-it rev-cdr)) ((begin (set-cdr! rev-it reved) (null? rev-cdr)) rev-it))))) (define reverse! nreverse) (define square (lambda (x) (* x x))) (define divides? (lambda (a b) (= (remainder b a) 0))) (define find-divisor (lambda (n test-divisor) (cond ((> (square test-divisor) n) n) ((divides? test-divisor n) test-divisor) (else (find-divisor n (+ test-divisor 1)))))) (define smallest-divisor (lambda (n) (find-divisor n 2))) ;; excluding "1" (define prime? (lambda (x) (= x (smallest-divisor x)))) (define gen-prime (lambda (hi) (let ((i (number-between 2 hi))) (assert (prime? i)) i))) (bag-of (gen-prime 20)) (display "===========================")(newline) (define (solve-partition-n n) (let ((x (number-between 1 n)) (y (number-between 1 n)) (z (number-between 1 n)) ) (assert (= (+ x y z) n) ) (list x y z) ) ) (bag-of (solve-partition-n 6)) (define (solve-confs-248) (let ((n (number-between 1 8)) (d (number-between 1 256)) ) (define m (expt (+ d 1) n)) (define v (if (> m n) m n)) (define t (+ n m v)) (assert (<= t 248)) (list n d m v t ) ) ) (define all-confs-248 (bag-of (solve-confs-248))) all-confs-248 'done (exit)

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how to use write to print string and character "normally" ?
by dillo gimp 27 Avr '07

27 Avr '07

hi how to use write to print string and character "normally" ? that is without the quotes and #\ ? Thanks.

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print vs. display segfault
by Lang Martin 27 Avr '07

27 Avr '07

ok, I got a segfault in a program and I don't quite understand the cause. This code: (define (string-escape string chars #!optional (escape (lambda (c) (print #\\ c))) port) (let ((pred? (%string-charset->pred chars)) (output (or port (open-output-string "")))) (with-output-port output (string-for-each (lambda (c) (if (pred? c) (escape c) (print c))) ; this is where the anti-magic happens string)) (or port (get-output-string output)))) is called many times (inside a function called sql-quote-object). On line 1420 of my input file, it segfaults. I've had a hard time reproducing this in a more confined context, but I will if this doesn't turn out to be known or easily deducible. If I change that (print c) to (display c), all is well. At first I was under the impression that the output was leaking because line 1421 turned out to contain a literal ^H. The progam exhibits the same behavior with all the lines containing control characters removed from the input. Also exhibits the same behavior in a file containing multiple copies of the first 1419 lines of the input, so I'm pretty confident it doesn't have anything to do with the input. I'm sorry this message is so rough -- I really will create a responsible bug report if this vague one doesn't give someone with a good understanding of the internals something to go on. Does print buffer it's output, by any chance?

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Big number Bug?
by dillo gimp 26 Avr '07

26 Avr '07

hi There might be a bug in big number handling, the same code runs fine under mzscheme and petite, but crashes with gambit : *** ERROR IN ##ratnum.* -- Divide by zero (quotient 0 0) I don't even use "quotient" in my code.

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how to use srfi-1?
by dillo gimp 25 Avr '07

25 Avr '07

hi how to use srfi-1? I usually do : (require (lib "list.ss" "srfi" "1")) what do I have to do when using gsc?

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got error from defining a vector?
by dillo gimp 25 Avr '07

25 Avr '07

(define b #(4 0 -8 -5)) /usr/4.0b22/bin/gsc accumu.sc *** ERROR IN "/lfs/scheme/accumu.sc"@946.11 -- Ill-formed expression

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