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2023-02-02.log
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<apteryx>I'm wondering if the nested 'begin' could cause problems? <apteryx>I think the error may have been misleading <mfiano>apteryx: what about doing what the manual suggests; ‘(setlocale LC_ALL "") ? <mfiano>Just wondering if that is the argument it is unhappy about. <apteryx>that code runs fine, I think the error was somewhere else, not sure what happened there <mfiano>Yeah strange. Error messages could shed some more context. <cow_2001>how do you remember all the eq? eqv? equal? semantics? <old>eqv is for equivalent <old>they are equivalent for an human, for example (eqv? "foo" "foo") <old>but in the machine they may not be the same object <old>eq? well typically a pointer comparaison, i.e. does these objects point to the same memory <cow_2001>comparing pointers is cheap, so it's short. how about this mnemonic? <old>The shorter the faster <old>yea it's like true equality <cow_2001>in ,describe eq? i see that (let ((n (+ 2 3))) (eq? n n)) is unspecified, so it ruins everything <cow_2001>"eqv? should be used for numbers and characters" but i don't see why the same n here shouldn't just return a #t <old>I'm pretty sure that (lambda (x) (eq? x x)) if #t no matter what <old>I'm no Scheme guru, perhaps someone know why <ArneBab>cow_2001: I just use equal? except if there’s a very special reason not to. <cow_2001>ArneBab: me too! but i still want to know ~_~ <cow_2001>i'm doing 1.20 in sicp. an exercise in patience. <ArneBab>cow_2001: ok :-) — eq? is "is" in other languages. It’s the most primitive. I don’t care about eqv? :-) <ArneBab>so my personal use cases are only equal? and eq? <old>typically eq? if want to check if it's the same reference <old>Which is great for symbol that are literal since they are interned <old>that allows for quick search in an associcatio map/list with a simple pointer comparison instead of strcmp for example <old>for number, always `=' when possible. All other cases, equal? <ArneBab>I really loved the little Schemer, by the way. <ArneBab>I regularly had lights of understanding going up in my mind while reading. <ArneBab>It’s awesome what they managed to create there. <mfiano>cow_2001: the length of the symbol's name <mfiano>eq? on a number doesn't make a lot of sense, because it is more or less checking that the pointer is same. <mfiano>and they are of arbitrary size, so can't be true <mfiano>A lot of places in the standard check the identity though <mfiano>In r7 at least. It's the only one I read so far :x <mfiano>old, cow_2001 The reason why eq? cannot be used reliably on numbers is because numbers larger than a machine word minus size of tag are big nums and consed on the spot, rather than immediate values. <cow_2001>i wish ,described said something about that <old>sure. But gotta to agree that (lambda (x) (eq? x x)) is #t <cow_2001>okay, for applicative order... err, no, for normal order evaluation there are 16 remainder calls! <old>even if x is big number <cow_2001>it's the same consed bignum (i don't really know how bignum work, but i understand they are compound data) <cow_2001>but same value bignums created in different places would have different areas in memory <cow_2001>so the example in ,describe is wrong? the let there is exactly your lambda, old <mfiano>big nums are just stored on the heap instead of the stack or directly in a register <mfiano>a bignum is a pointer to system memory. a non bignum is literal bits in program code. <ArneBab>cow_2001: describe sounds like numbers are a special case. Maybe because NaN cannot be equal to NaN <mfiano>more or less, depending on implementation <mfiano>You should never compare floats without an absolute and/or relative tolerance though... <mfiano>Good point though, even though I would never think to use exact comparison for a float <cow_2001>ArneBab: oh my gourd. trying to create NaN i see that nan is a procedure that creates nans. there is no such thing as a variable named NaN. <cow_2001>and this is much more detailed than i had thought <old>cow_2001: NaN has many representation bit wise <mfiano>Yeah of course, it's the same pointer <old>(/ 0.0 0.0) gives Nan <old>(eq? (/ 0.0 0.0) (nan)) => #f <old>(nan? (/ 0.0 0.0)) => #t <lloda>there's a literal nan, +nan.0, which should always be the same bits <ArneBab>(map (λ(comp)((λ(x) (comp x x)) (nan))) (list eq? eqv? equal? =)) ⇒ (#t #t #t #f) <lloda>but indeed if you get it through an op it could be anything <old>cow_2001: Believe me. Scheme actually got it right. Just look at the mess they've made in Javascript <old>a.k.a how to shoot yourself in the foot with a single character <old>the minus one bug equivalent in C <ArneBab>I have a fun commit in our company git repo: "mind the truthers!" — fixes an if(x) problem, because x could be "". <cow_2001>old: it's detailed because details matter <ArneBab>Until I hit that, I did not understand how well Scheme hat hit the right approach: only #f is #f. <old>ArneBab: Rust actually got it right too. True is true false if false <old>WAnt to test for string empty? Call the dang function <old>and it must return a boolean <cow_2001>if only rustlang wasn't curl | sh type of hack job <cow_2001>python is one big pile of unwraps and it's doing fine <cow_2001>i've forwarded something here and it's not yet here. strange <old>I meant that in Rust you need to unwrap every value wrapped in a Maybe type <old>Real nice for production I guess, real pain for quick prototyping and developing <cow_2001>then you grep all your unwraps and replace with something neater <cow_2001>no, it didn't work. maybe i'm somehow banned or quieted? <cow_2001>how do i check BrownJenkin's status in this channel? <old>Eeh I don't know what's BrownJenkin <old>sneek: seen BrownJenkin <cow_2001>very strange. i can see all messages but cannot write any. <old>I do see it in the users list <old>It's probably shadow banned? <mfiano>matrix does that often actually. sometimes i've seen a delay of 20 minutes. I stopped using it, and I pay less attention to [m] suffices if they conversation doesn't make sense, because I never know if I'm talking in real time or not <mfiano>I mean they got they R in IRC wrong :) <old>good reprenstation of what bash is <mfiano>Who knows. But it stands for real-time, which the matrix bridge frequently is far from. <cow_2001>why can't we have a good discord competitor ~_~ <cow_2001>wait, i've went too far away from guile and scheme <mfiano>k4m3n whoever you are, you revived r/guile with 2 days left to spare for being 1 year dead. <cow_2001>i've just had a bad idea. what if we had a (cut f <2> <3> <3> <1>) standing for (lambda (a b c) (f b c c a))? <ArneBab>old: but Rust is not from 1970, so it did not yet prove that it sticks to the right solution :-) <nckx>I'd certainly have made use of that bad idea in the past. <lilyp>cow_2001: That's not part of SRFI 26, but it is equivalent to C++'s std::bind IIRC <cow_2001>i hereby proclaim cutr and cuter as the weirdo <1> equivalent to cut and cute <cow_2001>now i just need to write the damned macros ~_~ <cow_2001>and i don't even know how to really write macros <mfiano>I found the r7 spec pretty nice for someone that never understood scheme style macros. <mfiano>as flatwhatson put it, it just gets right to the point. easy to read and find stuff. <mfiano>I think end of ch4 and beginning of ch5 explain macros and how to use them <mfiano>been a week or so but i think those chapters are correct <lloda>i haven't used bind in c++ since c++ got lambdas, and c++ lambdas are a lot clunkier than scheme's <wklew>cow_2001: as long as we give up complaining about haskell syntax forever :p <lechner>Hi, what's a reasonably simple way to obtain an HTML page title from a URL, please <lilyp>lechner: search for <title> and parse it as sxml or use htmlprag <mirai>lechner: what are you trying to parse <mirai>you can get the titles via bibtex, much better than regex'ing or sxml'ing HTML output <mirai>by "get the titles", you can use something that will read bibtex or plain regex <manumanumanu>Considering all the other macros I wrote back then it is amazing I got it to work. I even managed to write a decently efficient tree walker. <lechner>mirai / where may i find guile-bibtex, please? <lechner>mirai / yes, thank you for the suggestion! it just took me some time to figure that out myself :) <rekado>lechner: for arbitrary HTML (if no other structured format is available) I’d use htmlprag and sxpath <cow_2001>manumanumanu: everyone's on sourcehut? what about codeberg? i will look at the code and see if i get anything 