Gambit-list Mai 2009

gambit-list@iro.umontreal.ca

22 participants
44 discussions

Question on dynamic-wind
by Jeremie Lasalle Ratelle 29 Mai '09

29 Mai '09

I am trying to use dynamic-wind to execute code on thread suspension and thread restore but it doesn't seem to work. Is it possible or is there a way that I can do this? I need it to call a thunk just before it will call its continuation or just after it has been suspended. What is the correct way to do this?

1 0

define-type
by lowly coder 28 Mai '09

28 Mai '09

Hey, Where is define-type documented? I can't find it in r5rs or in the gambit documentation (though it is briefly mentioned in a tour of scheme through gambit). define-type is really cool and I'm starting to run against my limited knowledge of it. Thanks!

3 8

Viewing CPS expansion?
by James Long 25 Mai '09

25 Mai '09

`gsc' supports -expansion, but it seems to show the basic expansion into normalized gambit code. Is there any way to show the fully CPS-transformed forms of the code? Purely for research purposes. - James

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Closures, continuations, strategies, and actual measurements
by D.McClain 24 Mai '09

24 Mai '09

There is a very revealing paper by Clinger, Hartheimer, and Ost, "Implementations Strategies for First Class Continuations", that provides detailed examinations of various strategies, the code generated to support them, and actual measurements showing the effects of each implementation variation. http://www.springerlink.com/content/h5808n962434j275/fulltext.pdf This paper, along with Marc's recent explanation about the cost of CPS, should go a long way toward explaining why CPS code may be slower than direct form code. Dr. David McClain Sr. VP, Embedded Systems Asyrmatos Inc. Boston & Tucson phone: 520-529-2437 cell: 520-390-3995 web: www.asyrmatos.com e-mail: dbm(a)asyrmatos.com

3 5

for each, hash table, order
by lowly coder 23 Mai '09

23 Mai '09

i realize that order is fairly meaningless in the context of a hashtable however, if i for-each twice through a hashtable, and there are no writes (add or remove) to the hashtable in between them, am I, by the way that gambit is implemented, guaranteed to hit the elemements in the same order for the two times? thanks!

2 1

READ for things other than lists
by FFT 22 Mai '09

22 Mai '09

It appears that while WRITE works for just about anything, READ does not work for vectors, structures and probably other things. Is there a simple way to convince READ to recognize what WRITE has written? (Clojure does it)

2 1

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?

2 5

define-type with constraints
by lowly coder 21 Mai '09

21 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!

2 1

Vector of Scheme Objects
by lowly coder 21 Mai '09

21 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!

2 1

Bad version 3.0
by Frank Gizinski 20 Mai '09

20 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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Gambit-list Mai 2009