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2020-10-09 17:25:51 → snakemas1 joins (~snakemast@213.100.206.23)
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2020-10-09 17:43:18 <dwts> hi all, when a comparison returns GT, LT, or EQ, is it safe to assume that in reality the "real" values of them are numbers?
2020-10-09 17:43:33 <tomsmeding> dwts: the real values of what exactly
2020-10-09 17:43:37 <tomsmeding> GT/LT/EQ ?
2020-10-09 17:43:39 <dwts> yes
2020-10-09 17:44:01 <dwts> I have trouble understanding what is the benefit of returning these instead of numbers
2020-10-09 17:44:16 <tomsmeding> https://hackage.haskell.org/package/base-4.14.0.0/docs/Data-Ord.html#t:Ordering
2020-10-09 17:44:25 <tomsmeding> it's just 'data Ordering = LT | EQ | GT'
2020-10-09 17:44:48 <dsal> dwts: Why would you want a number there?
2020-10-09 17:44:49 <tomsmeding> though you can use fromEnum on them to get 0,1,2 if you should wish :p
2020-10-09 17:45:53 <tomsmeding> re:benefit: more type safety
2020-10-09 17:46:33 <tomsmeding> a number you can potentially confuse with something else that produces a number
2020-10-09 17:46:34 → todda7 joins (~torstein@athedsl-4367507.home.otenet.gr)
2020-10-09 17:46:34 <dwts> dsal: I don't *want* a number, I'm trying to visualize in my mind what haskell is doing underneath and why the ordering is implemented that way
2020-10-09 17:46:39 → thir joins (~thir@p200300f27f02580060eb7dde324e54c8.dip0.t-ipconnect.de)
2020-10-09 17:46:51 <dwts> ah, I see
2020-10-09 17:46:57 <tomsmeding> well deep down in the implementation details, Ordering really boils down to just a byte
2020-10-09 17:47:00 <tomsmeding> that's 0, 1 or 2
2020-10-09 17:47:10 <tomsmeding> because that's how haskell compiles down sum types like these
2020-10-09 17:47:20 <tomsmeding> but the programmer need not think about that :)
2020-10-09 17:47:46 <dsal> Similar to how Bool is False and True. You *can* convert those to numbers and some languages do that and it's massively error prone.
2020-10-09 17:48:22 × st8less quits (~st8less@2603:a060:11fd:0:9c66:9b18:c21:60c) (Ping timeout: 260 seconds)
2020-10-09 17:48:27 <dwts> do these LT/EQ/GT have a special name like True/False have Boolean?
2020-10-09 17:48:40 <Uniaika> hmm, not that I know of
2020-10-09 17:48:43 <tomsmeding> data Bool = False | True
2020-10-09 17:48:46 <Uniaika> they're just values of an ADT
2020-10-09 17:48:49 <tomsmeding> data Ordering = LT | EQ | GT
2020-10-09 17:48:51 <dsal> Ordering?
2020-10-09 17:48:56 <dwts> ok
2020-10-09 17:49:33 <dwts> I think I'm good for now, thank you all
2020-10-09 17:49:37 <dsal> Similarly, Boolean is often a really bad abstraction.
2020-10-09 17:50:05 <dwts> dsal: not sure why, but I have no reason not to believe you :)
2020-10-09 17:50:07 <dsal> I had an awful time understanding some of my own code that I modeled a bit from a protocol specification as a Boolean before I changed it to my own sum type and suddenly could read my own code.
2020-10-09 17:50:14 <dsal> boolean blindness is a terrible thing
2020-10-09 17:50:20 <tomsmeding> now we're (indirectly) talking about performance anyway: is there a faster way to read lots of Double's from a file than the following: sum . map (read @Double) . words <$> readFile "doubles.txt"
2020-10-09 17:50:30 <tomsmeding> because that's horribly slow
2020-10-09 17:50:59 <ski> @where boolean-blindness
2020-10-09 17:51:00 <lambdabot> http://existentialtype.wordpress.com/2011/03/15/boolean-blindness/
2020-10-09 17:51:02 → avdb joins (~avdb@ip-62-235-188-165.dsl.scarlet.be)
2020-10-09 17:51:03 <dsal> Is read that slow?
2020-10-09 17:51:08 <tomsmeding> apparently?
2020-10-09 17:51:45 <dsal> You could probably make a faster parser if you don't need all of the things that a Double parser could parse.
2020-10-09 17:52:36 <ski> > sortBy (comparing length <> compare) (words "The quick brown fox jumps over the lazy dog") -- dwts, with a separate `Ordering' data type, we can do this "primarily sort by length, secondarily by ordinary lexicographic word ordering")
2020-10-09 17:52:39 <lambdabot> ["The","dog","fox","the","lazy","over","brown","jumps","quick"]
2020-10-09 17:52:43 <tomsmeding> from some rudimentary timing the 'read' part indeed takes the longest time
2020-10-09 17:53:28 hackage rebase 1.10.0.1 - A more progressive alternative to the "base" package https://hackage.haskell.org/package/rebase-1.10.0.1 (NikitaVolkov)
2020-10-09 17:53:29 <tomsmeding> dwts: ski's example is a thing because we can define <> to do something special on Ordering that it does not do on plain numbers
2020-10-09 17:53:38 <dwts> ski: I was actually reading a book with a sortBy example and came to the definition of LT/EQ/GT
2020-10-09 17:54:03 <dwts> this looks really powerful and confusing at the same time
2020-10-09 17:54:14 × shafox quits (~shafox@106.51.234.111) (Remote host closed the connection)
2020-10-09 17:54:20 <tomsmeding> dsal: I could try that, but 'length . words' already takes longer than C++ takes to parse the entire thing into an std::vector<double>
2020-10-09 17:54:28 hackage rerebase 1.10.0.1 - Reexports from "base" with a bunch of other standard libraries https://hackage.haskell.org/package/rerebase-1.10.0.1 (NikitaVolkov)
2020-10-09 17:54:34 <tomsmeding> dwts: welcome to haskell :p
2020-10-09 17:54:42 <ski> @where monoids
2020-10-09 17:54:43 <lambdabot> comment on "Monoids? In my programming language?" by Cale in 2008 (or 2009 ?) at <http://www.reddit.com/r/programming/comments/7cf4r/monoids_in_my_programming_language/c06adnx> about a use of `
2020-10-09 17:54:43 <lambdabot> instance Monoid a => Monoid (rho -> a)'
2020-10-09 17:54:46 <ski> dwts ^
2020-10-09 17:55:24 <dsal> dwts: At a higher level, discussing meaning makes it a lot easier to reason about things than discussing implementation.
2020-10-09 17:55:59 <dwts> tomsmeding: thanks :P Coming from a scheme background some things are similar but others seem so different
2020-10-09 17:56:19 <dwts> dsal: I see your point
2020-10-09 17:56:20 <dsal> You never have to read the manual to remember what a compare function returns and how the integer value maps to maybe -1, 0, 1, or maybe just some negative or positive value, or 0, 1, 2, or how you might be able to combine comparisons by renormalizing them, etc...
2020-10-09 17:56:54 <dsal> The Ordering semigroup is really a secondary benefit. Primarily, you get to talk about what you mean instead of going back and forth to machine speak constantly.
2020-10-09 17:58:10 <dwts> hmmm
2020-10-09 17:58:15 <dwts> there's a lot to digest here
2020-10-09 17:58:16 <dwts> lol
2020-10-09 17:58:39 <tomsmeding> dwts: sidenote: "semigroup" means that definition of <>
2020-10-09 17:58:49 <tomsmeding> nothing more :p
2020-10-09 17:58:50 <dwts> ah
2020-10-09 17:59:51 <dsal> Well, what happens is when you start talking about what you mean, you get to make a lot of things common that you wouldn't have been able to see the commonality in before.
2020-10-09 18:00:01 × kers quits (~kers@178.162.212.214) ()
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2020-10-09 18:02:12 <galagora-> Has anyone ever used Silica, the lens library?
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2020-10-09 18:07:49 <dsal> galagora-: I just heard about it a around 5 minutes ago. Is it working out for you?
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2020-10-09 18:09:47 <tomsmeding> dsal: the same pipeline but then with Int instead of Double is only slightly faster (on a file that only contains integers, of course)
2020-10-09 18:09:56 <tomsmeding> so a custom Double parser is unlikely to make things better
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