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2016-05-01.log
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<ft>Then again, it would be possible to call a C compiler at compile time in a macro. <ft>But that seems tedious to write. <jmd>I want to creat the list ("x1" "x2" "x3" .... "xN") What is the quickest way? <df_>(map (lambda (x) (format #f "x~a" (+ x 1))) (iota n)) <linuxuser9000>Hi guys! I checked out guile after reading a post saying its new website is great. Question - could I work through SICP with guile-2.0 ? <wingo>linuxuser9000: you can, though there are some pieces of sicp that are not implemented in guile (the 'picture' language) <jmd>What is scm_c_with_continuation_barrier ? <df_>I did sicp in guile fwiw <jmd>There seems to be random calls to it. And it trashes memory which doesn't belong to it, causing segfaults. <df_>I hacked up a text-based version of the picture language <wingo>jmd: for all questions "what is FOO" where FOO is a procedure, the answer should be in the manual :) <jjk`>hello. is there a way to use normal xpath? (sxpath "//foo") for example? <wingo>i think so but i keep forgetting how to do it and the docs are terrible <jmd>Is there a general way to trace what the GC is doing? and why things are gettting collected? <jmd>I need to add an extra flag to a smob created with SCM_NEWSMOB (s_item, item_tag, x); How do I do it? <jmd>Note to wingo: Yes I have read the ****** manual. <jmd>Is this ^ a bug in Guile or in libgc ? <jmd>Or in soemthing else? <rain1>if you're still having to do work relating to gc stuff <jmd>If I'm reading those patches correctly they simply remove the freeb <jmd>It seems there are rather a lot of bugs in guile-ncurses :( <wingo>jmd: why would you ask what the function is, if it is documented in the manual? :) <wingo>your bug looks like some kind of memory corruption, which then fails during gc <wingo>but it doesn't mean that guile or gc has a bug. <wingo>because memory management is a cross-cutting concern, probably the problem is elsewhere. <wingo>some other c code that your program is using, where the c code has a bug in it. if it's guile-ncurses then probably it's there. <jmd>That is very likely. But I placed a watchpoint on the offending address to see what was mutating it. As you can see, in this case, guile-ncurses does not feature in the stack trace at all. It seems to be just guile and libgc itself which seems if the bug comes from elsewhere. <jmd>Regarding your question about that function. Although it is mentioned en-passant in the manual, there does not seem to be an entry in the API reference. Or in the index. At least I couldn't find one. <rain1>wingo: we're dealing with a badly designed library that does effects inside garbage collection handlers <jmd>It just mentions that scm_spawn_thread is called by this function. <jmd>df_: Great when you know where to look <wingo>i think what you meant to say was "yeah, you're right, i should have seen it" :-) anyways.... <wingo>i always use info, C-s in info leads me where i want :) <jmd>I'm on debian which doesn't have the info for Guile <jmd>and even if I install it manually, it sadly doesn't put in the topdir links. Once I tried fixing that manually and totally broke my system. <wingo>ACTION goodwill evaporating :P <rain1>"The lastest guile tarball uses revoked key" ? <ft>Debian has a separate package that contains the info manual, like guile-2.0-doc <jmd>ft: Do they now? I thought they were refusing to distribute them? <rain1>oh yeah debian... where the GNU free documentation license isn't free enough <janneke>guile-2.0-doc: /usr/share/info/guile-2.0.info-1.gz <jmd>df_: Right. They seem to have it now. Thanks <ft>It's part of the main repository too. <rain1>jmd: the idea of that patch I wrote is that it should free one from needing to think about GC semantics <df_>iirc, GFDL is ok with debian if there aren't invariant sections <df_>otherwise it goes in the non-free repo <df_>with the amusing side effect that vrms will complain to you about having gnu documentation installed <jmd>rain1: I see. Will it not also allow memory leaks? <rain1>jmd: well you do need to explicitly remove things (e.g. using delwin) <jmd>Anyway the bug I have right now seems to be a different one. <civodul>Guile's manual no longer has invariant sections and such, so there's no reason for it to be in Debian's "non-free" <rain1>I'm wondering about the revoked signature though <rain1>guile-ncurses is 12540 c + 4784 scheme <jmd>rain1: Right. It's bindings for the curses library. <ft>If the bindings have the same amount of lines of code as the original library, that seems like a bad deal. :) <df_>are you sure the original library isn't simply copied into the source tree? <rain1>that's a really good question! it's all new code though <ft>It doesn't afaics. The ncurses/ directory is full of SCM glue code. <civodul>rain1: isn't the C code somewhat generated? <rain1>I've not checked every file though <rain1>he does a lot of hard work building of a memory management guardians <jlicht>is there a clean way, in which to patch using patchelf an executable that is compressed and used as an origin? or should I then just make it a package instead? <jlicht>because decompressing the archive happens somewhere in the middle of the makefile, so I can't patch it after extracting b/c it is already humming along in the build phase <amz3`>this is code is dangerous, but I don't really know how to really get along without it <amz3`>btw I fixed the design of my blog :p <amz3`>What I need is to be able to execute queries against my UAV database <amz3`>instead of trying to come up with a turing complete query language I simply use scheme <amz3`>AND I will need to make sure that this databaser server is not accessible from outside of the machine... <amz3`>the snippet is only about the client/server eval thing <rain1>why does the query language need to be TC? <amz3`>I don't want to add procedures to the server database for everything thing I will need <rain1>maybe you could define a language and recognize it before allowing 'eval' <rain1>something like <safe-sexp> ::= (car <s>) | (cdr <s>) | ... etc. <rain1>just a really recursive function to ensure the input is acceptable <amz3`>I could make it so, but like i said I'm too lazy <amz3`>it's convenient to be able to execute anything server side :p <amz3`>OT, I did not do any post on the mailling on april, so I guess I will need to make two posts on may! <rain1>well just put it in a Docker container then <amz3`>I could also make sure nothing evil is in the environment passed to eval <amz3`>but I heared that this is not a proper sandbox <cojy>i thihink even just "read" is unsafe <rain1>a true sandbox would be great <amz3`>simple uav database server: done! <amz3`>(it more and more looking like a real database :D) <amz3`>(it's only lakes immutable in the name :P) <wingo>ACTION brain rotted by iconv, utf-blah and BOM codepoints <amz3`>next step, create the crawler logic... <jmd>amz3`: An immutable database is called a ROM. <amz3`>jmd: really? like RAM but it's dead, so it's called ROM? something like that? <jmd>Something like that, yes. <amz3`>yeah, I'm thinking about something alon the lines of datomic, not a ROM :p <amz3`>but right now, I don't have a usecase for an immutable database, and did not give much though either <amz3`>*If* I was going to build a banking application using Guile, I would go straight to an immutable database, but it's not the case :P <jmd>If a database is immutable, how can it be of any use? how does one enter data? <cojy>amz3`: persistent is a better word <cojy>jmd: it just means things aren't overwritten, they are added on <jmd>cojy: Older versions of Postgres used to do that. But they removed that feature unfortunately. <amz3`>getting the list of links in a (htmlprag) SXML using (sxml xpath) is quite simple: ((sxpath '(// a @ href)) sxml) <wingo>it's neat but i always forget how it works :) <wingo>ACTION still amused by guile's division of data structures into simple and compound <wingo>somehow a character set is a simple data structure, for the purposes of the manual :P <amz3`>i always forgot how it works too, but this time I got it working quickly :D <amz3`>sxpath document requires some love :) <wingo>contributions appreciated :) <amz3`>yeah, that would be really nice <wingo>could be you find ways the code could be better <amz3`>It's not an top of my priority list, because I first need to conquer the world... ;) <amz3`>sxpath doc is a not stepping stop of the priority task, right now... <amz3`>I'm trying to use another program from my scheme code, which takes as stdin a text file and outputs in stdout the processed file <amz3`>I'm trying to use `(open-input-output-pipe program)` but the program hangs indefinitly after I `(display "some string" port)` <rain1>maybe you need to close the port too <rain1>it could be waiting for more <amz3`>yes, but I need to read from the same pipe <amz3`>I should somehow tell the subprocess that stdin input is finished... <amz3`>I tried to do (display (eof-object) pipe) but it doesn't work <rain1>there are great docs inside xpath.scm <amz3`>(sxml xpath) it's clearly a powerful framework <rain1>yeah I loved xpath ever since I learned about it in perl! <rain1>"a nil nodeset is equivalent to #f in denoting a failure." <rain1>maybe it could be forced to always give #f in a later version <amz3`>Is it possible to provide stdin and retrieve stdout of program using Guile? <amz3`>using system* and providing string input and redirecting output to a string doesn't work <amz3`>I'm trying to wrap html2text <amz3`>I also take solution that replace html2text in pure scheme :) <amz3`>it extract links and every word bigger than 3 <amz3`>I mean words can appear multiple time, same for links <amz3`>it still requires some love, link appear relative to document and stuff <wingo>i am making progress with ports, it seems i can do the whole iconv thing eventually <wingo>it's nice to be able to rely on the presence of a port buffer we control; it can algorithmically improve some things <wingo>like being able to check EOF once for a four-byte utf-8 sequence instead of 4 times <wingo>or being able to peek without reading then unreading <wingo>i wonder if we can remove some of the more exotic port things from c, as if we replace them with scheme at boot-time, we can handle them there; and the relevant set of boot-time source code should all be valid utf-8 <cojy>is there any tools for generating ffi bindings from C headers? <wingo>cojy: that would be great but we don't have that right now; civodul used to have a larceny-like system <wingo>i have been using luajit's ffi recently and it's pretty great <wingo>a luajit-like ffi for guile would be great <wingo>ACTION forgot about (ice-9 iconv); neat <random-nick>doesn't luajit's ffi involve parsing C declarations? <wingo>well, that's part of it anyway <random-nick>hmm, luajit's FFI doesn't actually parse C headers it seems <random-nick>rain1: you basically give it C function, struct and type declarations that are required for interacting with the library and then it just allows you to interact with the library 