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00:08 brum: (define honestwork #f)
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02:07 vipjun: yes i should keep shoving the square peg into the round hole until it finally goes in.
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05:19 anonymou1: Hello everyone!
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05:19 anonymou1: I am reading Chapter 4.13: Dynamic Binding, parameterize
05:20 anonymou1: The parameterize form is not a binding form like let; each use of location above refers directly to the original definition. A parameterize form adjusts the value of a parameter during the whole time that the parameterize body is evaluated, even for uses of the parameter that are textually outside of the parameterize body:
05:20 anonymou1: Please tell me clearly
05:22 anonymou1: Is there difference (except as in just the text) in: (let ([a (make-parameter "b")]) BLA-BLA-BLA) and (parameterize ([a "b"]) BLA-BLA-BLA) and what is the difference
05:22 anonymou1: ?
05:24 anonymou1: ah, deep night in US...
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05:24 anonymou1: :(
05:25 anonymou1: how can I see the difference&
05:25 anonymou1: ?*
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09:12 martinux: hey. Can i make a mutable vector of size n in racket? Preferably all items in the vector should be #f initially
09:13 didi: rudybot: (make-vector 10 #f)
09:13 rudybot: didi: your sandbox is ready
09:13 rudybot: didi: ; Value: #(#f #f #f #f #f #f #f #f #f #f)
09:13 didi: martinux: ^
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09:19 martinux: didi: thanks a bunch
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11:03 didi: If I'm creating a new exception structure to a library and I'm using `exn:fail' struct as its super, should I name it `exn:fail:my-exception' or just `my-exception'?
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11:06 asumu: didi: I'd go with `exn:fail:my-exception`
11:08 didi: asumu: Yeah, that's what I'm thinking too. Although I'm a little concern about symbol clashing. Maybe prefixing `my-exception' with the library's name, but that might be too much.
11:09 asumu: If this is in a library, your library's client can just (require (prefix-in ...))
11:10 adu: is this possible? http://paste.lisp.org/display/135609
11:10 didi: asumu: Thanks.
11:10 asumu: adu: no, I don't think so. Why not just have (assign op a b)?
11:11 didi: adu: Looks like you want `setf'.
11:11 adu: oh, I guess that would make more sense
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11:16 adu: thanks
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11:41 asumu: Seen on twitter: http://jvjulien.free.fr/Informatique/Racket/racket.htm#distance-ville
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11:49 DaniG2k: guys Im trying to do something super simple in racket but
11:49 DaniG2k: its the first time i use it and cannot understand the syntax too well
11:50 asumu: DaniG2k: ask away.
11:50 Cryovat: asumu: That's wonderfully concise :D
11:50 asumu: Cryovat: :D
11:50 DaniG2k: i want to make a loop from x to y with a step z
11:50 rich2: DaniG2k: range(x y z)
11:50 DaniG2k: should i use cond for this or just if?
11:51 mithos28: DaniG2k: (in-range 0 10 2)
11:51 asumu: rudybot: (for/list ([i (in-range 1 10 2)]) i)
11:51 rudybot: asumu: your sandbox is ready
11:51 rudybot: asumu: ; Value: (1 3 5 7 9)
11:51 rich2: e.g. (map my-special-func (range 0 10 1))
11:51 asumu: DaniG2k: ^ for example
11:52 DaniG2k: hm what if I want to use recursion here? that's what i was trying to do
11:52 DaniG2k: range is probably better but
11:52 rich2: asumu: i'm a beginner too, is there a preference when to use for/list compared to map?
11:52 DaniG2k: i just want to get a feel for making the function
11:52 didi: DaniG2k: Use `if'.
11:52 rich2: i guess for/list is when you don't care about the result as map builds the result list
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11:52 mithos28: rich2: If you are going to write an anonymous function, then for/list is usually easier to read
11:53 mithos28: rich2: for/list builds a list, for does not
11:53 asumu: rich2: for/list is more general, since you can traverse more than just a list or several lists.
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11:55 Cryovat: Plain for feels a bit un-FP
11:55 asumu: DaniG2k: if you know how to write a `map` or `for-each` function using recursion, then this problem reduces to writing a function that builds a list of numbers in the range you want.
11:55 mithos28: Cryovat: That may be because its only use is effects
11:56 Cryovat: Yeah, my Lisp teacher instilled a deep fear of anything that might look imperative in me :D
11:57 didi: Cryovat: They might hate CL's `LOOP' then.
11:57 asumu: Sometimes you just need to print stuff.
11:58 anonymous97890: Hello everyone!
11:58 asumu: Hi.
11:58 anonymous97890: I am installing 5.3.3
11:58 anonymous97890: If you want to install new system links within the "bin" and "man" subdirectories of a common directory prefix (for example, "/usr/local") then enter the prefix of an existing directory that you want to use.  This might overwrite existing symlinks, but not files.
11:58 anonymous97890: (default: skip links) > /usr/local/bin
11:58 anonymous97890: "/usr/local/bin/bin" does not exist, skipping.
11:58 anonymous97890: "/usr/local/bin/share/man/man1" does not exist, skipping.
11:58 anonymous97890: Installation complete.
11:58 anonymous97890: not great! It was a typo
11:58 anonymous97890: That's not critical for me, but it could be better
11:59 anonymous97890: Is anyone agreed/disagreed here?
11:59 rich2: is there a generic function similar to 'for/list' but uses a "window". e.g. (windowed-loop F '(1 2 3 4)) would produce F(X, 1), F(1 2), F(2 3), F(3 4), F(4 X)
11:59 asumu: Is the problem that the install script didn't detect that "/usr/local/bin" was a typo?
11:59 rich2: i need a variant with window size 2 and 3
12:00 rich2: i'm trying to write it myself - but at least rackunit and check is good :)
12:00 anonymous97890: asumu: I think he should suggest me to correct or ask if I sure.
12:00 anonymous97890: am*
12:01 anonymous97890: Please tell me if you disagree.
12:01 asumu: I don't think the install script can be smart enough to figure out if you typoed or not.
12:01 anonymous97890: with*
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12:03 anonymous97890: asumu: he skipped. He didn't do thing I asked him to do. He has some (better than nothing) idea - to not do anything, but that's strange since I've told him to.
12:04 rich2: i thought i could use foldl for the 2 wide window - but foldl uses the result from the previous call rather than the next element
12:04 anonymous97890: Ok, doesn't matter. Thank you for your opinion, that's not critical for me, just a little suggestion, I expected it can be good.
12:04 anonymous97890: could*
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12:05 DaniG2k: guys
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12:06 anonymous97890: ?
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12:10 asumu: rich2: maybe iterate through the list and use `(take lst 2)` at each step? Stop when the list has fewer than 2 elements (and handle the first and last elements specially).
12:10 asumu couldn't think of a more elegant way off the top of his head
12:11 rich2: asumu: good idea, i'll try that. my way of (rest (rest x)) was failing at the end and i couldn't think of how to get round it
12:12 rich2: sorry (first (rest x))
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12:33 anonymous97890: I have just tried to use "#lang slideshow". I wrote (circle 10) and executed. It worked. I closed DrRacket without saving. Then I done the same, but I saved the code. After I closed DrRacket(both times), and runned it again - I #lang racket was runned.
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12:33 anonymous97890: s/I /
12:33 anonymous97890: The Guide says: If you’ve used DrRacket before with something other than a program that starts #lang, DrRacket will remember the last language that you used, instead of inferring the language from the #lang line.
12:34 anonymous97890: here: http://docs.racket-lang.org/guide/intro.html
12:34 anonymous97890: Should I send a bugreport?
12:34 bremner: there are some settings about that.
12:34 bremner: check the detailed language settings.
12:35 mithos28: #lang slideshow is not a language in the sense that that sentence is using the word
12:35 anonymous97890: mithos28: I tried #lang scribble/base before it - the same effect
12:35 anonymous97890: bremner: did the Guide lie to me?
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12:35 anonymous97890: if it lies, should I send a bugreport?
12:35 mithos28: that when you reopen drracket it opens with #lang racket
12:36 mithos28: like I said, the individual #lang lines are not languages in the sense that that sentence is using the word
12:36 anonymous97890: mithos28: I've tried scribble/base and slideshow. Give me, please an example of a language they meant
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12:36 asumu: anonymous97890: notice that that sentence says "other than a program that starts #lang".
12:36 mithos28: pretty big, htdp
12:37 asumu: i.e., if you are using #lang, this does not apply (since DrRacket infers the language from source).
12:38 jbclements: to be (slightly) more precise: if you are using #lang and DrRacket is set to "Use language declared in program…". Right?
12:38 asumu: (yes, what jbclements said)
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12:39 RacketCommitBot: [racket] plt pushed 1 new commit to master: http://git.io/2bus2A
12:39 RacketCommitBot: racket/master 200c209 Matthias Felleisen: make read-csv-file/rows available in BSL; closes PR 13542
12:39 (part) RacketCommitBot
12:40 anonymous97890: ah, yes! Thank you.
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12:40 anonymous97890: very much
12:40 bremner: right, that's what I meant about detailing language settings
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13:47 rich2: i think i've done it and although my basic tests pass, i'm still not confident
13:48 rich2: i've called it windowed-map except the function takes 2 (previous and current) arguments instead of 1 (current)
13:49 didi: rich2: I coded one too if you want to take a look. :^)
13:49 rich2: didi: ooh i'd like to, i'll paste mine somewhere - any criticism or pointers of mine would be helpful
13:51 didi: rich2: http://paste.kde.org/678614/
13:57 rich2: http://paste.opensuse.org/69718557
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14:01 rich2: didi: is the n parameter meant to be fixed at 2? it errors if i use 3
14:01 didi: rich2: Really? It shouldn't. :^(
14:01 didi: (map-window list 42 3 (list 1 2 3 4)) => '((42 1 2) (1 2 3) (2 3 4) (3 4 42))
14:02 rich2: ah correct, it was cons in mine
14:02 didi: :^)
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14:02 didi: (map-window + 42 3 (list 1 2 3 4)) => '(45 6 9 49)
14:03 stamourv: rudybot: (define l '(1 2 3 4))
14:03 rudybot: stamourv: your sandbox is ready
14:03 rudybot: stamourv: Done.
14:04 stamourv: rudybot: (for/list ([x l] [y (rest l)]) (cons x y))
14:04 rudybot: stamourv: ; Value: ((1 . 2) (2 . 3) (3 . 4))
14:04 stamourv: rich2: ^
14:04 stamourv: Pad the list if you want `(X . 1)' and `(4 . X)'.
14:05 rich2: stamourv: tidy solution - i think i need to learn for/list
14:06 rich2: could for/list work for a window of 3
14:06 stamourv: rich2: Sure.
14:06 stamourv: rudybot: (for/list ([x l] [y (rest l)] [z (rest (rest l))]) (list x y z))
14:06 rudybot: stamourv: ; Value: ((1 2 3) (2 3 4))
14:07 stamourv: asumu: Re distance-ville: This is pretty awesome.
14:07 (join) RacketCommitBot
14:07 RacketCommitBot: [racket] plt pushed 1 new commit to master: http://git.io/4KR0Ow
14:07 RacketCommitBot: racket/master 7558eb4 Danny Yoo: Conditionally link to the SRFI docs on docs.racket-lang.org when rendering PDFs....
14:07 (part) RacketCommitBot
14:07 rich2: that's what i missing earlier, when i was using (first (rest x)) and (rest (rest x)) it was erroring (correctly) due to them being empty
14:11 samth: stamourv: can you translate it for us?
14:12 stamourv: samth: Sure, what do you want to know?
14:12 stamourv: The first example computes the distance between 2 cities.
14:12 samth: stamourv; not sure, just a summary
14:12 dented42: when using define-relation in redex, what's the difference between ⊂ and ⊆ in the contract?
14:13 stamourv: samth: The second displays a graph of the water level of a given french river.
14:13 stamourv: The third shows a live count of the twitter followers an account has.
14:13 didi: rich2: http://paste.kde.org/678662/
14:13 stamourv: The fourth is a live graph of wind speed.
14:14 stamourv: And the last is a barometer.
14:14 didi: rich2: Nah, it's wrong.
14:14 didi: rich2: Sorry.
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14:15 samth: stamourv: pretty cool
14:15 samth: thanks
14:17 stamourv: It's especially cool that each of these is only about a dozen lines.
14:17 stamourv: Racket is pretty awesome.
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14:21 asumu: dented42: I suspect there is no difference, but this is just a conjecture.
14:21 dented42: ok
14:22 dented42: I'm looking over the source, and there doesn't seem to be one.
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14:25 rich2: i'm struggling a bit with for/list - i think for/list (for 2 lists anyway) "zips" the 2 together, so the 1st element of both are picked, then the 2nd of both, and this happens min(length(list1), length(list2)) times
14:26 rich2: i;m confused with stamourv: answer above (for/list ([x l] [y (rest l)]) (cons x y))
14:26 rich2: because y will "run out" of elements before x
14:29 rich2: ah think i got it now
14:30 dyoo_: rich2: yeah, the the for loops do parallel iteration.  The for* loops do nested iteration
14:30 rich2: he's "moving y down" compared to x, then "zipping"
14:31 rich2: so for*/list would be a cartesian product
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14:34 paddymahoney: question-what do you all do while recompiling racket?
14:35 dyoo_: paddymahoney: I usually keep two copies of racket around, so I can continue working.  :)
14:36 (quit) dyoo_: Quit: dyoo_
14:36 paddymahoney: great answer! I need a second anyways to do scripting on the first :)
14:36 rich2: i was actually going to search for how to do a cartesian product in the general sense and for*/list does it :)
14:39 rich2: other languages don't really have an excuse for not having features do they, because if they made their languages rewrite/transform into racket they'd get them
14:39 rich2: e.g. var x = y; print(x); -> (let ([x y)) (print x))
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14:42 rich2: i wonder how bad it would be if some languages targeted a lower level language but still high level rather than basically assembly language/CIL etc
14:43 dyoo: rich2: I've been actually thinking about what it would take to do an llvm backend for racket.
14:45 rich2: dyoo: i guess a lot, no? would racket gain anything in terms of extra analysis or performance before hitting the CPU?
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14:46 dyoo: Perhaps.  But it would also mean I get to obsolete Whalesong, since there's an llvm->js thing out there called Emscripten.  :)
14:47 dyoo: (or, at the very least, retarget Whalesong so it emits llvm code instead of the crazy-silly intermediate language it's generating now.)
14:48 rich2: nice, theres a lua interpreter based from emscripten
14:49 dyoo: so yeah, I've started to look at Eric's work with llvm bindings in https://github.com/shekari/racket-llvm
14:49 rich2: *penny drop - we could get racket in the browser?
14:50 rich2: great work dyoo:
14:50 dyoo: Would like that.  Currently doing http://wescheme.org with that goal in mind.
14:50 paddymahoney: that would be quite cool.
14:52 rich2: although with everything rewriting to javascript - what does javascript rewrite into? it's missing several features i like from racket at least - bignums for 1
14:53 rich2: do browsers still lock everything when javascript executes ?
14:53 dyoo: rich2: https://developer.mozilla.org/en-US/docs/DOM/Using_web_workers
14:54 dyoo: not necessarily anymore.  And you can still play some tricks to avoid blocking the browser even in a single-threaded world by trampolining.
14:55 rich2: thanks
14:55 dyoo: example:
14:56 dyoo: http://www.wescheme.org/openEditor?publicId=GLQfrukW1L
14:56 dyoo: Press "Run", and you should see cpu usage go high
14:56 dyoo: but you can still press break to interrupt the computation.
14:56 dyoo: (I mean, you can press "Stop")
14:57 rich2: so is that wescheme or the browser allowing the Stop?
14:58 dyoo: wescheme is periodically abandoning the current computation, saving it in a callback, and then giving control back to the browser.
14:58 rich2: ah
14:58 dyoo: the browser then restarts the trampoline at some point.  Between that period, you can interact with gui elements, so the browser doesn't get locked up.
15:00 dyoo: rich2: re bignums, there are several bignum libraries for javascript now
15:00 dyoo: WeScheme uses: https://github.com/dyoo/js-numbers
15:00 dyoo: and I know of at least two other bignum libraries out there.  So that's not an issue anymore.  ;)
15:00 paddymahoney: How widely used is the browser/ collection?
15:01 dyoo: unknown
15:01 paddymahoney: k
15:01 dyoo: historically, it was used for Help Desk, if I recall correctly.
15:01 rich2: kudos on your project!
15:02 dyoo: But got replaced by an external browser call at some point
15:03 paddymahoney: I see. I'm beginning work on migrating it, and wondering if I can replace the MZSCHEME= attribute with RACKET= attribute
15:04 paddymahoney: If a lot of external libs use it, I'll add a RACKET tag alongside the first, deprecate MZSCHEME=
15:04 dyoo: I'd recommend asking racket-dev about this one; I'm clueless.
15:06 paddymahoney: dyoo: k thanks for the info!
15:10 paddymahoney: is anyone aware of a racket/gui signature that obseletes mred/mred-sig?
15:12 dyoo: paddymahoney: hmm, no….   doing a quick scan
15:13 dyoo: couldn't find anything useful
15:14 paddymahoney: neither. I guess it stays then.
15:15 (quit) keppy: Ping timeout: 255 seconds
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15:45 (part) epta
15:47 jaimef: how hard would it to be to decompile a binary compiled from a .rkt?
15:47 asumu: jaimef: you could `raco decompile`
15:48 jaimef: oh
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16:01 rich2: does anyone use the drracket debugger?
16:02 rich2: i'd like a breakpoint rather than stepping over everything until the point i'd like to stop
16:03 (quit) ijp: Ping timeout: 252 seconds
16:03 (nick) ijp` -> ijp
16:04 dyoo: rich2: according to http://docs.racket-lang.org/drracket/debugger.html?q=debugger#(part._.Definitions_.Window_.Actions)
16:04 dyoo: you should be able to set breakpoints
16:06 dyoo: Do you see the pink circle when you hover over an expression's open paren?
16:08 rich2: dyoo: fantastic, yes
16:09 rich2: from the manual though for drracket i can't get "M-C-f : move forward one S-expression" to work, i keep getting the windows start menu appearing
16:10 rich2: i'm pressing ESCAPE-CTRL-F
16:10 rich2: as "On Windows and Mac OS X, Meta is only available through the Escape key."
16:10 dyoo: hmmm… checking something.
16:11 dyoo: In Preferences/General, is there something about meta keys there?
16:11 dyoo: Under Mac OS X, there's "Treat command key as meta"
16:11 dyoo: but I don't know what the situation's like on Windows.
16:12 rich2: i can't see it in the pref dialog
16:12 dented42: preferences -> editing -> general
16:13 rich2: yeh i looked in pref -> editing -> general, and pref -> general - i'm on windows xp sp3
16:13 samth: dyoo: almost certainly whalesong will be saner targeting JS directly than using something like emscripten/LLVM/asm.js
16:16 dyoo: samth: maybe.  I do want to look at it regardless of practicality, and at the worst, I learn something new.  :)
16:18 dyoo: rich2: for the combo ESCAPE-CTRL-F, are you tapping the escape key once, and then chording  the control-f?
16:18 dyoo: rich2: it's following Emacs conventions in the absence of a separate meta key
16:19 (join) DaniG2k
16:19 DaniG2k: can someone plz explain let let* and letrec to me a bit better
16:19 DaniG2k: i dont quite get it
16:20 rich2: if i tap ESC, then CTRL+f, my cursor disappears
16:20 rich2: DaniG2k: use let* if the 2nd id references the 1st for example
16:21 rich2: eg. (let* ([x 1] [y (+ x 1]) (display y))
16:22 rich2: oops. should be (let* ([x 1] [y (+ x 1)]) (display y))
16:23 DaniG2k: ok so if i just use let then it doesn't reference the x
16:23 DaniG2k: what about letrec?
16:23 rich2: no - they are all "invisible" to each other in let - as i understand it
16:23 DaniG2k: still gives me two
16:23 rich2: letrec is like let* but can go both ways i think
16:24 dyoo: DaniG2k: in letrec, where you have something like (letrec ([f <some-expression>]) …)
16:24 DaniG2k: dyoo: the documentation says its similar to let, not let*
16:24 (join) rohni
16:24 dyoo: in <some-expression>, you get to refer to the thing being bounded, f
16:24 jbclements: DaniG2K: in a letrec, all of the names bound by the letrec are in scope for all of the right-hand-sides of all of the bindings.
16:25 dyoo: so it's meant for things like recursive function definitions.
16:25 jbclements: DaniG2K: … though that doesn't mean that they've been evaluated yet.
16:25 rich2: DaniG2k: i was wrong about letrec, sorry.
16:26 jbclements: rudybot: (letrec ([even (lambda (x) (if (= x 0) #t #f))] [odd (lambda (x) (if (= x 0) #f #t))]) (odd 15))
16:26 rudybot: jbclements: your sandbox is ready
16:26 rudybot: jbclements: ; Value: #t
16:26 (quit) gridaphobe: Remote host closed the connection
16:26 jbclements: ouch! just kidding.
16:27 (join) gridaphobe
16:27 jbclements: rudybot: (letrec ([even (lambda (x) (if (= x 0) #t (odd (- x 1))))] [odd (lambda (x) (if (= x 0) #f (even (- x 1))))]) (odd 15))
16:27 rudybot: jbclements: ; Value: #t
16:28 jbclements: DaniG2K: in the example I just gave rudybot, the function 'even' is allowed to refer to 'odd', even though its binding appears later.
16:28 (join) jonrafkind
16:29 DaniG2k: jbclements: ok i see
16:29 DaniG2k: thanks
16:30 jbclements: first time I've used rudybot. That was awesome! :)
16:30 (quit) gridaphobe: Remote host closed the connection
16:30 DaniG2k: what's rudybot
16:30 dyoo: rudybot: what on earth are you?
16:30 rudybot: dyoo: Those lying "scientists" and their "theory of gravity" say that the earth is solid.
16:30 dyoo: see, that's rudybot.  :)
16:31 DaniG2k: :P
16:31 dyoo: it's an IRC bot that says ridiculous things.  And sometimes it evaluates racket expressions.
16:31 dyoo: rudybot: (+ "4" 2)
16:31 rudybot: dyoo: your sandbox is ready
16:31 rudybot: dyoo: error: +: contract violation <NEWLINE>   expected: number? <NEWLINE>   given: "4" <NEWLINE>   argument position: 1st <NEWLINE>   other arguments...: <NEWLINE>    2
16:32 DaniG2k: rudybot: '("test")
16:32 rudybot: DaniG2k: your sandbox is ready
16:32 rudybot: DaniG2k: ; Value: ("test")
16:32 DaniG2k: cool :D
16:32 dyoo: danig2k: https://github.com/offby1/rudybot
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16:36 (join) moe_4715
16:36 moe_4715: hi guys
16:36 iartarisi: hi! I'm just starting out with racket and am trying to use a redis library. One of the functions returns #\nul . What am I supposed to do with this value? or what kind of value is it? Where can I read more about it.
16:36 (join) whoops
16:36 dyoo: iartarisi: it's a character if I'm reading it right
16:37 dyoo: iartarisi: http://docs.racket-lang.org/guide/characters.html#%28tech._character%29
16:37 iartarisi: it's just like that, no quotes or anything
16:37 dyoo: More specifically, a unicode character point.
16:37 iartarisi: ah
16:38 moe_4715: i need your help for the following problem:
16:38 dyoo: In that specific case, it looks like it's ascii character 0.
16:38 iartarisi: so should I just run with it and do (char=? #\nul result) all over the place? or patch the library to return null instead?
16:39 dyoo: I'm not too familiar with redis.  Where can I find out about it?
16:39 iartarisi: dyoo: http://redis.io/
16:39 iartarisi: dyoo: from what you're saying I guess it might be part of its protocol to return ascii character 0
16:39 (join) quidnunc
16:40 moe_4715: i need a function where the input is a stream and the output is a stream with pairs of the input stream with ("hi" streamval)
16:40 moe_4715: here is my code: http://pastebin.com/VvMDXPym
16:40 dyoo: How should the null character be interpreted in this key/value store?  Yeah, I'm not sure what it means semantically.
16:40 iartarisi: dyoo: no idea, I don't know much about the internal protocol, but I guess it's time to learn some. Anyway, thanks a lot!
16:40 (join) RacketCommitBot
16:40 RacketCommitBot: [racket] plt pushed 2 new commits to master: http://git.io/GW3ixQ
16:40 RacketCommitBot: racket/master 17d6e16 Robby Findler: minor clarifications of the docs (that would have helped me...
16:40 RacketCommitBot: racket/master d403f3c Robby Findler: add docs to address how image equality, rounding, and alpha values...
16:40 (part) RacketCommitBot
16:40 moe_4715: please hlp!
16:41 moe_4715: i'm very desperate about the problem
16:41 jbclements: moe_4715: purpose statement? test cases?
16:42 samth: jbclements: the one-trick-tutor :)
16:42 jbclements: samth: purpose statement? test cases?
16:43 (join) jonrafkind
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16:44 quidnunc: Can someone tell me what I am doing wrong in this simple macro? http://paste.lisp.org/display/135614
16:44 moe_4715: one moment, please
16:46 dyoo: quidnuc: does not compile.  I don't know what lim is
16:46 dyoo: so perhaps your macro isn't actually being loaded.
16:47 (join) gridaphobe
16:47 moe_4715: http://pastebin.com/6kHjxERC
16:47 quidnunc: dyoo: should be x
16:47 quidnunc: sorry
16:48 quidnunc: I'm using geiser and C-x C-e doesn't seem to work all the time
16:48 moe_4715: that means for any input element it should output the same element paired with the value 0
16:49 moe_4715: let me say the input steram would be (1 stream), it would produce ((0 . 1) stream) out of it
16:49 jbclements: moe_4715: nice! not quite runnable test cases, but I think I see where you're going.
16:50 quidnunc: dyoo: So it does work, it was just as you said that the form wasn't loaded
16:50 quidnunc: dyoo: thanks
16:50 (join) keppy
16:50 dyoo: :)
16:50 moe_4715: then i am relieved :)
16:50 quidnunc: :(
16:50 jbclements: moe_4715: …. aaaaand, I've got to go run to get on a bus. Sorry!
16:50 didi: quidnunc: Are you evaling it in a visited file?
16:50 (part) jbclements
16:50 moe_4715: noooo :(
16:50 didi: quidnunc: If that's the case, you have to enter it first.
16:50 quidnunc: didi: yes
16:51 moe_4715: when are you back?
16:51 quidnunc: didi: Yes I have entered it
16:51 didi: oic
16:51 didi: quidnunc: So that's all I know.
16:51 didi: :^)
16:54 rich2: just wondering, why is range an open boundary - it catches me out everytime as i;m used to mathematica range. e.g Range[1, 10] -> [1..10], but (range 1 10) -> [1..9]
16:55 paddymahoney: is anyone else finding that Reindent All in DrRacket is causing right-ward creep in scribble files with @name[something]{} forms?
16:55 (join) RacketCommitBot
16:55 RacketCommitBot: [racket] plt pushed 1 new commit to master: http://git.io/qeYoIg
16:55 RacketCommitBot: racket/master b40e38b Robby Findler: fix documentation errors...
16:55 (part) RacketCommitBot
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17:04 jonrafkind: whats the parameter to change the scribble font size
17:06 moe_4715: who of you can tell me how to define a stream with tuples in it?
17:07 moe_4715: i need to get a stream with e.g. (1 . stream) and need to make ('(0 . 1) . stream)
17:08 moe_4715: and then output the result for this
17:08 quidnunc: Is geiser-doc-symbol-at-point supposed to not contain actual documentation?
17:08 moe_4715: has anyone an idea how to do that?
17:08 didi: quidnunc: It has different results for guile and racket.
17:11 moe_4715: can anyone help?
17:12 didi: moe_4715: Do you know how to do it with lists?
17:13 moe_4715: i think so. maybe by doing (cons  0 (car <mylist>))
17:14 moe_4715: sorry, (cons (cons  0 (car <mylist>)))
17:14 didi: Nice.
17:14 moe_4715: and then  the cdr... i forgot
17:15 moe_4715: but the same must be feasible with streams...
17:16 moe_4715: but the bad thing at it is that i can not assign a single element to a string-cons
17:16 paddymahoney: is there a way to figure out the safest amount of memory that the DrRacket limit can be set to, given the amount of OS memory? Anyone else with ridiculously high limits set?
17:16 (join) cdidd
17:20 didi: moe_4715: IIUC your problem, you can do it using the same method you would use with lists, just changing the appropriate procedure to one that operates at streams.
17:20 DaniG2k: guys i wrote a small function that takes a stream and returns a list of the values in the stream in order
17:21 DaniG2k: but my function sucks
17:21 (join) ijp`
17:21 DaniG2k: when i run it with a test stream that computes powers of two it freezes so easily
17:21 moe_4715: didi: which one would that be in this case?
17:21 moe_4715: didi: when i use stream-cons, i can only pass 2 streams
17:23 DaniG2k: http://hpaste.org/82861
17:23 DaniG2k: why is it so slow?
17:25 (nick) ijp` -> ijp
17:27 iartarisi: if (require json) doesn't work, does it mean I need a newer racket?
17:28 iartarisi: I'm on 5.2.1
17:28 moe_4715: think i got it
17:28 moe_4715: how can s.o. get the value out of an #<procedure:...irst_section.rkt:103:28>
17:28 moe_4715: sequence?
17:30 moe_4715: (stream-append(cons 0 (stream-first pr))) --> thought that this would give me a stream??
17:31 jaimef: if you had a week off to focus on learning racket enough to be dangerous what path would you take?
17:34 rich2: jaimef: learning racket from scratch?
17:35 jaimef: had many stabs at it, have the little schemer books.
17:35 jaimef: some elisp experience
17:35 jaimef: but still very new
17:37 rich2: i've never done any lisp/scheme before but used other languages - i'm just pretending i'm in my old language and converting at the moment, so i start with define/let/lambda/map/range
17:37 rich2: and setting little problems - that take about a screenful of code
17:37 jaimef: ahh
17:38 moe_4715: why this does not work?
17:38 moe_4715: (stream-first(stream-cons(cons 0 (stream-first ones)) (stream-rest ones)))
17:38 moe_4715: any idea?
17:38 moe_4715: ones is (define ones (lambda () (stream-cons 1 ones))) in this case
17:39 (join) cnonim
17:39 rich2: jaimef: you have any actual programs/scripts you need written? if so that'd be a good goal
17:39 (join) mizu_no_oto
17:39 jaimef: rich2: yeah I have some ideas
17:40 jaimef: racket was the only scheme I could find that would load this 13meg json file properly
17:40 moe_4715: (stream-cons(cons 0 (stream-first ones)) (stream-rest ones)) -> #<stream> ... but i am not able to apply stream-first
17:41 rich2: for example 1 problem i set myself in racket was to find the next 4 repeating digit prime numbers after the sequence, 2,3,5,7,11 - a repeating digit prime is a number expressed in decimal every  digit is exactly the same
17:42 cnonim: how i can escape format string? (format "~a~a" "foo") == "foo~a"
17:42 rich2: only takes a couple of lines but gets you thinking of how the syntax and library functions co-operate
17:42 (quit) cdidd: Ping timeout: 248 seconds
17:43 asumu: rudybot: (format "~~a~a" "foo")
17:43 rudybot: asumu: your sandbox is ready
17:43 rudybot: asumu: ; Value: "~afoo"
17:43 asumu: cnonim: ^
17:44 rich2: 13meg json - how long that take to parse?
17:44 cnonim: thx
17:44 asumu: moe_4715: I don't understand the question
17:44 asumu: rudybot: (define ones (lambda () (stream-cons 1 ones)))
17:44 rudybot: asumu: Done.
17:44 asumu: rudybot: (stream-first(stream-cons(cons 0 (stream-first ones)) (stream-rest ones)))
17:44 rudybot: asumu: error: stream-first: contract violation <NEWLINE>   expected: (and/c stream? (not/c stream-empty?)) <NEWLINE>   given: #<procedure:ones>
17:44 asumu: Oh, well, ones is not a stream.
17:44 asumu: It's a thunk.
17:45 asumu: rudybot: (define ones (stream-cons 1 ones))
17:45 rudybot: asumu: Done.
17:45 asumu: rudybot: (stream-first(stream-cons(cons 0 (stream-first ones)) (stream-rest ones)))
17:45 rudybot: asumu: ; Value: (0 . 1)
17:46 moe_4715: oh, nice... then maybe you can also help me qith my problem... can i give you some code to check?
17:46 asumu: iartarisi: I don't think 5.2.1 has json. IIRC it was around 5.3.
17:47 moe_4715: here is my code: http://pastebin.com/htEDtnqV
17:47 cnonim: 'temp-dir points to /var/tmp ... which kind of find-system-path points to /tmp ?
17:47 iartarisi: asumu: thanks, I went with (planet mordae/redis:1:1)
17:47 moe_4715: it takes a stream, e.g. (1 . stream) and must return ('(0 . 1) . stream)
17:48 moe_4715: but this function returns a procedure instead of the wanted stream
17:48 (quit) stchang: Read error: Operation timed out
17:48 (quit) iartarisi: Remote host closed the connection
17:50 moe_4715: i need to call (stream-add-zero ones) and get back some stream
17:50 moe_4715: but it returns a procedure
17:51 asumu: The spacing and the indentation there makes it pretty hard to read. I recommend putting spaces between parens.
17:51 asumu: Also I think this is just the same issue. A thunk is not a stream.
17:51 asumu: rudybot: (stream? (lambda () 5))
17:51 rudybot: asumu: ; Value: #f
17:52 asumu: rudybot: (stream? (lambda () (stream-cons 5 empty-stream)))
17:52 rudybot: asumu: ; Value: #f
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17:55 (quit) Kaylin: Quit: Leaving.
17:55 moe_4715: pls can someone help?
17:56 moe_4715: asumu: do you have any idea how to solve this?
17:56 asumu: moe_4715: see ^
17:57 (join) cdidd
17:58 moe_4715: asumu: maybe there is a problem with the pr assignment?
18:00 asumu: I have to head out for dinner, but see my comments above. Cheers.
18:06 (join) anRch
18:07 dented42: I'm looking but can't find one, is there a way to convert a string into a syntax object? parsing the string through the reader and using datum->syntax would destroy the information that makes syntax objects interesting, like line numbers and positions and whatnot.
18:09 jonrafkind: read-syntax should preserve that information
18:10 jonrafkind: and also do datum->syntax for you
18:10 jonrafkind: i think read is normally implemented as (syntax->datum (read-syntax))
18:11 dented42: oh ok, I was looking in the wrong place.
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18:27 moe_4715: how can i take this code and modify it so that it returns a stream instead of a procedure? http://pastebin.com/pTyPXgZ2
18:29 (join) mizu_no_oto
18:31 paddymahoney: moe_4715: http://pastebin.com/bKzK2PKx
18:31 (quit) mizu_no_oto: Client Quit
18:32 moe_4715: paddymahoney: what did you change?
18:33 paddymahoney: moe_4715: f returns lambda's within each branch of the cond-these were removed.
18:33 moe_4715: ah, that's the trick.... thank you very much :)
18:33 paddymahoney: replaced with the expressions they thunk...
18:34 (quit) merijn: Ping timeout: 252 seconds
18:35 (quit) acarrico: Read error: Operation timed out
18:37 moe_4715: paddymahoney: can you please tell me hot so can check if a stream is finished?
18:38 moe_4715: i tried (null? (stream-first (pr) but think this is not correct
18:38 didi: rudybot: (require racket/stream)
18:38 rudybot: didi: your sandbox is ready
18:38 rudybot: didi: Done.
18:39 paddymahoney: moe_4715: http://docs.racket-lang.org/reference/streams.html?q=stream&q=drracket%3Atool^
18:39 rudybot: http://tinyurl.com/b8ahulq
18:39 didi: rudybot: (stream-empty? '())
18:39 rudybot: didi: ; Value: #t
18:41 moe_4715: paddymahoney: have you seen the error message? http://pastebin.com/HfWCTKuM
18:41 moe_4715: do you know why pr is suddenly a procedure?
18:42 moe_4715: that seems strange to me
18:45 didi: moe_4715: http://paste.kde.org/678854/
18:45 (join) merijn
18:49 DaniG2k: why is it so slow?
18:50 moe_4715: didi: this is my problem in this case http://pastebin.com/iVR5h32x
18:51 moe_4715: and i'm currently working on it for 5 hrs
18:51 moe_4715: this drives me completely crazy
18:52 (quit) cnonim: Quit: WeeChat 0.4.0
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18:54 didi: moe_4715: http://paste.kde.org/678860/
18:56 (quit) anRch: Quit: anRch
18:56 didi: DaniG2k: `cons' will not delay the evaluation.
19:01 didi: rich2: re: range <http://www.cs.utexas.edu/users/EWD/transcriptions/EWD08xx/EWD831.html>
19:01 (quit) andres-v`: Ping timeout: 244 seconds
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19:06 dyoo: moe_4715: I haven't been following the thread here.  It looks like you're doing streams?  Which kind of streams?  for SICP, or are you using the streams in the Racket standard library, or…?
19:07 (quit) DaniG2k: Read error: Connection reset by peer
19:10 (quit) rich2: Quit: Leaving.
19:11 dyoo: Unfortunately, my brain melted.  Need to take a break. :)  Talk later!
19:12 (quit) dyoo: Quit: dyoo
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19:22 DaniG2k: what's the key for multiline comments in racket?
19:22 didi: DaniG2k: #| |#
19:23 didi: Nah. #| #|
19:23 DaniG2k: thanks
19:23 DaniG2k: didi: first one was correct
19:24 didi: DaniG2k: Yeah, brain fart. Sorry.
19:24 DaniG2k: lol
19:26 (quit) jonrafkind: Ping timeout: 255 seconds
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19:39 DaniG2k: if I have (define x 5)
19:39 DaniG2k: how can I negate x?
19:39 DaniG2k: just (- x) ?
19:41 jonrafkind: yes
19:41 jonrafkind: but the result will not be permanent
19:41 jonrafkind: do you want x to now store -5?
19:43 DaniG2k: hmmmm
19:43 DaniG2k: im not sure
19:43 DaniG2k: i have to write a stream
19:43 DaniG2k: that just prints out numbers from 1 to n
19:43 (quit) mizu_no_oto: Quit: Computer has gone to sleep.
19:43 DaniG2k: and if the number mod 5 is 0 then i need to return the negation of that number
19:43 DaniG2k: so I have
19:44 DaniG2k: (define number-stream
19:44 DaniG2k: (letrec ([f (lambda (x) (cons x (lambda () (if (= (remainder x 5) 0) (- x) (+ x 1)))))])
19:44 DaniG2k: (lambda () (f 1))))
19:44 (quit) ambrosebs: Remote host closed the connection
19:45 DaniG2k: doesn't seem to be working too well tho
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19:47 SunMoonStar: Can you use a let expression in a cond branch to be evaluated before the predicate?
19:48 jonrafkind: you can use it in the predicate
19:48 SunMoonStar: My issue is that I don't want an expression evaluated until a certain branch, but once I get to the branch, it will have to be evaluated multiple times after
19:49 jonrafkind: (cond [(let ([x 5]) (= x 5)) ...])
19:49 jonrafkind: oh you want a let expression in the middle of some predicates?
19:49 jonrafkind: (cond [p1 p2 (let ...) p3 p4]) ?
19:49 jonrafkind: hm i see what you're saying
19:49 (quit) bitonic: Ping timeout: 248 seconds
19:50 jonrafkind: i would use nested cond's I guess
19:50 paddymahoney: moe_4715: http://pastebin.com/fbSj2rU9
19:50 jonrafkind: (cond [p1 p2 (else (let ... (cond ...))])
19:50 SunMoonStar: Er, I think the first thing you said may be the answer. The problem to state more clearly is that it is evaluated in the branch predicate to see if it is true or false, but i want that to be the last time it is evaluated so that I don't have to eval it anymore because it will be used multiple times
19:50 jonrafkind: and a macro to make it look nice
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19:51 jonrafkind: maybe (cond [p1 p2 [let x1 ...] p3 p4) where `let' is a keyword that macro knows about
19:51 jonrafkind: and it will produce hte nested conds for you
19:51 jonrafkind: where p3 and p4 are in the scope of the x1 binding
19:51 SunMoonStar: let's not go into macros yet ;P I'm not that far along
19:51 jonrafkind: well without macros you can still do a let + nested cond
19:52 jonrafkind: or actually theres another strategy -- use force/delay
19:52 jonrafkind: you can do (let ([x (delay ...)]) (cond [p1 p2 (force x)])
19:52 jonrafkind: so delay makes x not be evaluated until the first force, then each subsequent force wont re-evaluate x, it will just get the value immediately
19:53 SunMoonStar: hm yes
19:53 SunMoonStar: but I don't know about else syntax in a cond statement. I have to look that up. I wanted to know if there was another way besides delay/force
19:53 (quit) Kaylin: Quit: Leaving.
19:53 jonrafkind: else just looks like any other predicate clause
19:54 jonrafkind: (cond [(blah?) ...] [else (printf "i got here")])
19:54 SunMoonStar: ok so is else always the last branch?
19:54 jonrafkind: except obviously `else' is not evaluated
19:54 jonrafkind: yea
19:54 SunMoonStar: I was taught to use #t for the last branch
19:54 jonrafkind: ah
19:54 SunMoonStar: But anyway that does not matter, so else will not help me. I am trying to understand your other solution
19:54 jonrafkind: i guess theres no semantic difference, just using 'else' looks better
19:55 jonrafkind: and it has to be last, whereas #t can appear anywhere
19:55 (quit) bitonic: Ping timeout: 255 seconds
19:55 SunMoonStar: so this?: (07:50:18 PM) jonrafkind: (cond [p1 p2 (else (let ... (cond ...))])
19:55 jonrafkind: yea
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19:56 SunMoonStar: If there are only 2 branches, is it preferable to use if over cond?
19:56 jonrafkind: yea
19:57 SunMoonStar: I learned how to implement force and delay but is that in the language
19:57 jonrafkind: its in racket
19:57 SunMoonStar: ok
19:57 jonrafkind: are you using a student language?
19:57 SunMoonStar: No I'm learning racket
19:57 paddymahoney: moe_4715: http://pastebin.com/mY3jGcig
19:57 jonrafkind: its in racket/promise and racket
19:57 SunMoonStar: I will go with force/delay I feel like that is probably a perfect use case for it
19:57 jonrafkind: yes i think its better than nested conds
19:58 jonrafkind: although i dont know if theres an extra computational overhead..
19:58 jonrafkind: but likely its small anyway
19:58 SunMoonStar: thanks
19:58 SunMoonStar: i love irc
19:59 jonrafkind: mos def
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20:02 DaniG2k: guys
20:03 (join) xulfer
20:05 paddymahoney: DaniG2k: hi
20:06 DaniG2k: hello
20:06 DaniG2k: I'm trying to get this function to work
20:06 DaniG2k: it's quite simple
20:06 DaniG2k: just prints out numbers from 1 to n
20:06 DaniG2k: but if n%5 == 0 then it prints out -n
20:06 DaniG2k: quite simple
20:06 DaniG2k: making it a stream
20:07 DaniG2k: so i have
20:07 DaniG2k: (define number-stream
20:07 DaniG2k: (letrec ([f (lambda (x) (cons x (lambda () (if (= (remainder x 5) 0) (f (- x)) (f (+ x 1))))))])
20:07 DaniG2k: (lambda () (f 1))))
20:07 DaniG2k: that's my stream
20:07 DaniG2k: but when i try using it
20:07 DaniG2k: i am getting values like
20:07 DaniG2k: '(1 2 3 4 5 -5 5 -5 5 -5 5)
20:07 DaniG2k: it's getting stuck
20:08 paddymahoney: so you know the problem is in the true branch of your if statement.
20:08 DaniG2k: yeah
20:08 (quit) jeapostrophe: Ping timeout: 276 seconds
20:08 DaniG2k: I tried with something like
20:08 DaniG2k: (- (+ x 1))
20:09 DaniG2k: still doesn't work
20:09 DaniG2k: i get
20:09 DaniG2k: '(1 2 3 4 5 -6 -5 4 5 -6 -5)
20:10 paddymahoney: well, think about what you want-a stream with the negative of the number, stream-cons'ed to the rest of the stream.
20:11 paddymahoney: (stream (- x) (stream-rest s)
20:11 paddymahoney: )
20:11 paddymahoney: sorry, (stream-cons (- x) (stream-rest s))
20:11 DaniG2k: so the problem is with (cons x...)
20:11 (join) ijp
20:12 paddymahoney: I believe so. if number-stream is a stream and not a list, it needs to be constructed as a stream-cons, not cons.
20:13 paddymahoney: but it is difficult to work without the entirety of the code.
20:14 DaniG2k: paddymahoney: http://hpaste.org/82872
20:15 DaniG2k: paddymahoney: that will just print out the numbers from 1 to n in a strea
20:16 DaniG2k: stream
20:16 DaniG2k: but i will edit it now
20:16 DaniG2k: with an if statement
20:16 DaniG2k: (if (= (remainder x 5) 0) negate x, otherwise (+ 1 x))
20:17 DaniG2k: thats what i think i need
20:17 DaniG2k: but im not sure
20:19 paddymahoney: ah-are you building your own streams again?
20:19 paddymahoney: are you in the same class as moe_4715?
20:19 DaniG2k: hmm not sure
20:19 DaniG2k: who that is
20:20 ozzloy: you want to negate x if it's divisible by 5?
20:20 DaniG2k: yeah
20:20 ozzloy: otherwise add 1 to x?
20:20 DaniG2k: (if (= (remainder x 5) 0) (- x) (+ x 1))
20:20 ozzloy: what are you doing?
20:20 DaniG2k: but it gets stuck in a loop
20:20 DaniG2k: when i run
20:20 DaniG2k: (stream-for-n-steps funny-number-stream 11)
20:20 DaniG2k: i get
20:21 DaniG2k: '(1 2 3 4 5 -5 5 -5 5 -5 5)
20:21 DaniG2k: so its getting stuck
20:21 ozzloy: negative 5 is divisible by 5
20:21 ozzloy: so it gets negated
20:21 ozzloy: to 5
20:21 ozzloy: which is divisible by 5
20:22 DaniG2k: ah
20:22 DaniG2k: touche'
20:22 DaniG2k: (= (remainder (- 5) 5) 0)
20:22 DaniG2k: #t
20:22 DaniG2k: hmm
20:22 DaniG2k: so I'll have to return that and then add +1
20:22 ozzloy: you can also do -5
20:22 ozzloy: as the literal -5
20:23 DaniG2k: yeah
20:23 DaniG2k: but
20:23 DaniG2k: i cant do that on variables
20:23 ozzloy: x
20:23 ozzloy: yeah
20:23 DaniG2k: i need to call (- x)
20:23 DaniG2k: got it
20:23 ozzloy: just making sure.  so what sequence are you aiming for?
20:24 DaniG2k: something like
20:24 DaniG2k: '(1 2 3 4 -5 6 7 8 9 -10)
20:24 DaniG2k: easy
20:24 DaniG2k: except for this negation :\
20:24 DaniG2k: so ill have to cons the (- x)
20:24 DaniG2k: and then move up one
20:25 ozzloy: looks like you maybe want one variable that counts, and another variable that gets added to the list, based on the count
20:25 DaniG2k: jeez all these parentheses are tiring
20:25 ozzloy: or at least, that's what i'd do
20:25 DaniG2k: ozzloy: but i dont need to count since it's a stream
20:25 DaniG2k: another function takes care of counting
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20:26 ozzloy: so you have one function take care of counting, and another function that computes what gets added to the list, based on that function
20:26 ozzloy: right now you're messing with the counting
20:26 ozzloy: or so it seems
20:27 DaniG2k: ok i think i figured it out
20:27 DaniG2k: i need a cond
20:27 ozzloy: oh, for the parens, i've not been too troubled by them, and i think it's because i started off using paredit mode in emacs from the beginning of my entry in to the lisp world
20:27 DaniG2k: if it's (negative? x) then make it positive and add one
20:27 DaniG2k: i think that should solve it
20:28 ozzloy: i almost always type open parens, and almost never type negative parens
20:28 ozzloy: er... close parens
20:30 ozzloy: i take it from the paste url that you use haskell?
20:30 ozzloy: i would like to learn haskell
20:30 ozzloy: i started reading learn you a haskell, seemed neat
20:31 ozzloy: wasn't high priority enough for me to stick with it at the time, though
20:31 (join) firefux
20:32 DaniG2k: nah using racket
20:32 ozzloy: ic
20:32 ozzloy: btw, you can use rudybot to do some stuff
20:33 ozzloy: rudybot, (display "hello world!\n")
20:33 rudybot: ozzloy: your sandbox is ready
20:33 rudybot: ozzloy: ; stdout: "hello world!\n"
20:37 DaniG2k: im close
20:38 DaniG2k: getting '(1 2 3 4 5 -6 7 8 9 10 -11)
20:38 (quit) gridaphobe: Remote host closed the connection
20:39 DaniG2k: bah
20:39 DaniG2k: i'll do this tmrw
20:39 DaniG2k: night all!!
20:39 (quit) DaniG2k: Quit: Leaving
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21:46 jaimef ponders converting some awk over to racket for log parsing to sqlite
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21:57 offby1: probably doable
21:58 offby1: I added sqlite stuff into rudybot a while ago, and it was pretty easy.
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22:06 asumu: jaimef: there is http://docs.racket-lang.org/mzlib/mzlib_awk.html
22:06 asumu: Though I'm not sure it does exactly what you'd want.
22:06 asumu: And it should be revived and lifted out of mzlib if it's useful.
22:11 wdkrnls: how would you extend '+ to work with programmer defined data types?
22:12 offby1: I wouldn't.
22:12 offby1: Next question :)
22:12 wdkrnls: say I define a currency data type $ and I want to add two different data types.
22:12 wdkrnls: (+ ($ 10) ($ 20)) => ($ 30)
22:12 wdkrnls: :P
22:13 offby1: why not just add 10 to 20 and call it good? :)
22:13 asumu: wdkrnls: you can't do this with +, but in general you can use the racket/generic library to write such generic functions.
22:13 offby1: seriously, I think most schemers would write an "add-currency" function
22:13 (quit) ambrosebs: Remote host closed the connection
22:14 offby1: wdkrnls: next step: (+ (kg 2) (lbs 3)) => 7.4lbs
22:14 wdkrnls: offby1: exactly!  my emacs calc does it, why not racket!?
22:16 (quit) acarrico: Ping timeout: 264 seconds
22:16 wdkrnls: asumu: is this because + isn't a function?
22:16 wdkrnls: asumu: like with or/and?
22:17 offby1: wdkrnls: I suspect it's a pretty hard problem -- but possibly worth doing.
22:17 asumu: rudybot: eval (require (prefix-in : +)) (struct foo (x)) (define (+ a b) (if (and (foo? a) (foo? b)) (+ (foo-x a) (foo-x b)) (:+ a b))
22:17 rudybot: asumu: error: #<undefined>:1:43: read: expected a `)' to close `('
22:18 asumu: rudybot: eval (require (prefix-in : +)) (struct foo (x)) (define (+ a b) (if (and (foo? a) (foo? b)) (+ (foo-x a) (foo-x b)) (:+ a b)))
22:18 rudybot: asumu: error: #<undefined>:1:22: +: standard-module-name-resolver: collection not found <NEWLINE>   collection: "+" <NEWLINE>   in collection directories: <NEWLINE>    /mnt/racket-5.3.2/collects <NEWLINE>   in: +
22:18 (quit) rmathews: Quit: ...
22:19 asumu: rudybot: eval (require (prefix-in : racket)) (struct foo (x)) (define (+ a b) (if (and (foo? a) (foo? b)) (+ (foo-x a) (foo-x b)) (:+ a b)))
22:19 rudybot: asumu: Done.
22:19 asumu: rudybot: (+ (foo 5) (foo 8))
22:19 rudybot: asumu: ; Value: 13
22:19 asumu: wdkrnls: ^
22:19 wdkrnls: asumu: awesome!
22:19 Nisstyre-laptop: rudybot: (thread (lambda () 3))
22:19 rudybot: Nisstyre-laptop: your sandbox is ready
22:19 rudybot: Nisstyre-laptop: ; Value: #<thread>
22:20 asumu: Though it's not necessarily a good idea... overloading + can be confusing.
22:20 asumu: wdkrnls: Also, + is a function, but it's not defined as a generic one so you can't use racket/generic.
22:21 Nisstyre-laptop: just do what offby1 said and write currency-add
22:24 (quit) cataska: Remote host closed the connection
22:25 Nisstyre-laptop: you can define it pretty concisely too, if you have "on": (define $-add (compose $ (on + $-n)))
22:25 Nisstyre-laptop: on is "(define $-add (compose $ (on + $-n)))"
22:26 Nisstyre-laptop: er, (define (on f g)  (λ (a b) (f (g a) (g b))))
22:29 wdkrnls: on seems pretty cool, but even a decent currency function should have units and must take on the additional complexity of the time value of money.
22:29 wdkrnls: so, the problem is more like the physical units one offby1 mentioned.
22:29 Nisstyre-laptop: that is a good point
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22:40 wdkrnls: would it be possible to make racket return $10 or 10lb and have it understand that it is a specific data type, much like numbers?
22:43 wdkrnls: then I could evaluate expressions like: ($-add $10 €5)
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22:47 offby1: I've always wanted values with units; I don't know of any language that has 'em
22:50 Fare: units? what kind of units?
22:50 offby1: pounds, dollars, etc
22:50 Fare: caml had units, maybe does again.
22:50 Fare: frink has units
22:50 Fare: F# has units.
22:50 offby1: really?
22:50 Fare: there may be a racket extension with units, for all I know
22:51 Fare: and maybe some macro systems for CL or Scheme.
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22:58 doomrobo: how do I match a parentheses with a regex?
22:59 doomrobo: I tried #rx"(" and #rx"\(" and neither work
22:59 doomrobo: *open parenthesis
22:59 mithos28: #rx"\\("
22:59 doomrobo: why the double \?
23:00 mithos28: so \ is used as the escaping character in string literals
23:00 mithos28: so you need \\ to have a single \ in the actual string
23:00 doomrobo: ah, ok
23:00 mithos28: and \ is also used as the escaping characters in regexps
23:01 mithos28: and ( is special in regexps for matching groups
23:01 mithos28: rudybot: (regexp-match #rx"(.*)34" "1234")
23:01 rudybot: mithos28: your sandbox is ready
23:01 rudybot: mithos28: ; Value: ("1234" "12")
23:01 doomrobo: yeah, that part was familiar
23:02 (quit) keppy: Ping timeout: 264 seconds
23:02 doomrobo: also, where is string-split located? It's not in racket/string
23:03 mithos28: it is
23:03 mithos28: rudybot: doc string-split
23:03 rudybot: mithos28: http://docs.racket-lang.org/reference/strings.html#(def._((lib._racket%2Fstring..rkt)._string-split))
23:03 mithos28: http://docs.racket-lang.org/reference/strings.html#(def._((lib._racket/string..rkt)._string-split))
23:04 mithos28: offby1: you still around?
23:04 doomrobo: rudybot: (begin (require racket/string) (string-split "hello world"))
23:04 rudybot: doomrobo: your sandbox is ready
23:04 rudybot: doomrobo: ; Value: ("hello" "world")
23:04 doomrobo: odd, it gives me an undefined reference in my version
23:05 mithos28: what version are you using?
23:05 mithos28: I think it is a recent addition
23:05 doomrobo: 5.2.1
23:05 mithos28: yeah its newer than that
23:05 doomrobo: gotcha
23:05 mithos28: you can do regexp-split
23:05 mithos28: or just update
23:05 doomrobo: heaven forbid
23:06 Fare: [(] is a good way to escape the (, too
23:07 (join) keppy
23:07 Fare: nicer than \\
23:07 Nisstyre-laptop: Fare: just use a character class you mean?
23:07 doomrobo: ohai Nisstyre-laptop
23:07 Fare: no, a singleton list of characters
23:08 Nisstyre-laptop: Fare: how does that apply to regexps?
23:08 doomrobo: Nisstyre-laptop, #rx"[(]"
23:08 mithos28: Fare: That is a character class
23:09 doomrobo: I think that is a character class Fare
23:09 Nisstyre-laptop: doomrobo: yeah a character class
23:09 Fare: whatever you call it
23:09 Nisstyre-laptop: a character class is sort of like a set
23:10 Fare: character class - string prototype - rune pattern - glyph object - sacred cow
23:12 Fare: codepoint set - letter recognizer - law officer
23:12 doomrobo: pilcrow
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23:48 paddymahoney: Is anyone here familiar with units? I think I am running into a bug.
23:48 mithos28: paddymahoney: you mean like racket/unit? A bit.
23:49 paddymahoney: mithos28: right-racket/unit
23:49 paddymahoney: mithos28: I am running into an error that looks like:
23:50 (quit) rmathews: Quit: ...
23:50 paddymahoney: mithos28: define-unit/new-import-export: identifier exn:file-saved-instead1 is not present in old exports in: (define-unit/new-import-export browser@ (import setup:plt-installer^ mred^ url^) (export browser^) ((hyper^ html-export^ bullet-export^) pre-browser@ setup:plt-installer^ mred^ url^))
23:51 paddymahoney: mithos28: problem-there is no identifier named exn:file-saved-instead1 -> it is named exn:file-saved-instead, and I have confirmed that the sigs and exporting unit refer to it as such.
23:51 mithos28: That does seem like a bug
23:52 mithos28: It is also over my head in terms of what you are doing with the units
23:52 paddymahoney: mithos28: ah k-thank you for your time :)
23:52 paddymahoney: I'm going to look into it further-it only came up upon migrating to racket/unit from scheme/unit
23:53 mithos28: what is using units?
23:53 paddymahoney: browser collection.
23:53 paddymahoney: I'm working on a fork to move the code to racket.
23:54 paddymahoney: it is pretty much done I think, aside from this issue.