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2020-09-20 16:48:02 <sm[m]> lechner: you're right, it's not crystal clear, but yes I'm 99% sure it descends. Probably you tested it by now
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2020-09-20 16:53:42 <nshepperd2> whoa i just converted this dynamic programming-based tokenization thing from a laziness based pure Vector implementation to a mutable unboxed vector in ST, and it got like 100 times faster
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2020-09-20 16:54:39 <ski> top-down to bottom-up ?
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2020-09-20 16:55:52 <nshepperd2> I'm not quite sure what those terms mean, but yes I think so
2020-09-20 16:57:15 <nshepperd2> the lazy one was let table = V.generate (n+1) go; go = ...; in table!n
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2020-09-20 16:57:45 <nshepperd2> the fast one was to make a mutable unboxed vector and fill it out in order from 0 to n
2020-09-20 16:57:49 <ski> where `go' referred to `table'
2020-09-20 16:57:55 <nshepperd2> yeah
2020-09-20 16:58:17 <sshine> >_<
2020-09-20 16:58:24 <ski> hm, what kind of access pattern ?
2020-09-20 16:59:25 <nshepperd2> 'go i' would reference some or all cells between i-5 and i-1
2020-09-20 16:59:34 <hekkaidekapus> sm[m]: The 1% wins again :p It does not descend. At its core, the function calls doesFileExist to the supplied dirs.
2020-09-20 17:00:12 × ajfelfjlsdkfjejf quits (~jfkeflkwe@2600:1700:4640:c560:68bd:9d76:dbd8:24e7) (Quit: Leaving)
2020-09-20 17:00:20 <hekkaidekapus> doesFileExist (dir </> file)
2020-09-20 17:00:24 <ski> "bottom-up" means that you fill in the "lower cells", before the higher ones, "prematurely" so to speak. "top-down" that you start demanding higher ones, which in turn demands lower ones (which are cached)
2020-09-20 17:00:39 <dolio> There's a lot of overhead in the top-down lazy approach.
2020-09-20 17:00:54 <dolio> If you're working with integers.
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2020-09-20 17:01:47 <nshepperd2> ski: then yeah, that's exactly what i did
2020-09-20 17:01:59 <ski> nshepperd2 : i suppose you could even use a five-tuple, or a vector of size five, then
2020-09-20 17:02:41 × kenran quits (~maier@b2b-37-24-119-190.unitymedia.biz) (Ping timeout: 260 seconds)
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2020-09-20 17:03:37 <dolio> Yeah, like computing fibonacci with an accumulator pair.
2020-09-20 17:04:10 <ski> (you'd use `mod i 5')
2020-09-20 17:05:09 <ski> i suppose the computation of the next cell isn't a linear function of the previous five ones ..
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2020-09-20 17:07:20 <ski> nshepperd2 : probably the lazy approach would work better, in case there's many cells which aren't needed to compute the result
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2020-09-20 17:08:11 <dolio> Yeah, there are a lot of factors making it sub-optimal for this case.
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2020-09-20 17:10:10 × cheater quits (~user@unaffiliated/cheater) (Read error: Connection reset by peer)
2020-09-20 17:10:37 <sshine> I have a data type, data Foo a = X a | Y a | Z a | P | Q | R; and I'd like to make a type NumFoo = forall n. Num n => Foo n, but it seems that I can't do that. what are my alternatives? I was thinking of a data type with a type class constraint.
2020-09-20 17:10:59 <sshine> I think I can use GADTs, but that would require me to alter 'Foo', too, right?
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2020-09-20 17:11:55 <nshepperd2> ski: yeah in this case pretty much all cells are eventually needed
2020-09-20 17:13:30 <ski> sshine : why can't you ?
2020-09-20 17:13:33 <hyperisco> sshine, what is the idea of this type? I don't understand
2020-09-20 17:14:26 <ski> a value of type `NumFoo' possibly contains a number of any numeric type the user wants to get
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2020-09-20 17:22:54 <zebrag> I believe `cons :: a -> List l a -> List (Succ l) a` cannot be done with plain GADT? (The following ref, might suggest it could be done?? https://www.cis.upenn.edu/~sweirich/talks/GADT.pdf, page 9)
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2020-09-20 17:23:45 <hyperisco> zebrag, is there a compiler error you're seeing?
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2020-09-20 17:24:18 <zebrag> At least if you consider `Succ` is a data constructor
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2020-09-20 17:24:39 <zebrag> hyperisco: no I'm just reading the slides above
2020-09-20 17:25:59 <hyperisco> all I don't understand is how that is an example of dependent types
2020-09-20 17:26:07 × tzh quits (~tzh@2601:448:c500:5300::ad1c) (Ping timeout: 260 seconds)
2020-09-20 17:26:20 <hyperisco> what is your objection?
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2020-09-20 17:29:08 <Cale> sshine: Just replace "type NumFoo = ..." with "data NumFoo = ..." and what you wrote is valid code, if a little bit useless. Forgetting everything about the type of number except that it was a type of number will mean that you can't really do a whole lot with it (in particular, you won't know that it's the same type as any other type of number, so the arithmetic you can perform is very limited)
2020-09-20 17:30:13 <Cale> sshine: Or did you really want to define a type synonym for the universal type?
2020-09-20 17:31:09 <c_wraith> Cale: it's a bit worse than that since Show is no longer a superclass of Num. Num doesn't give you any eliminator to see the value.
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2020-09-20 17:31:18 <Cale> Right
2020-09-20 17:31:27 <Cale> and Eq is gone too
2020-09-20 17:31:48 <c_wraith> Eq would be pretty useless, though, unless you wanted to test for lack of reflexivity or something
2020-09-20 17:32:16 <Cale> You could test out arithmetical identities involving your one value of the given type :)
2020-09-20 17:32:41 <c_wraith> hah. is x + x == x ? :)
2020-09-20 17:32:45 <Cale> yeah
2020-09-20 17:33:08 <hyperisco> no
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2020-09-20 17:33:43 <Cale> (that's essentially the same as checking if x == 0, if the instance is lawful)
2020-09-20 17:33:48 <c_wraith> I suppose the Num instance would let you throw in literals too, so you could ask if x * 0 == x
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2020-09-20 17:34:21 <c_wraith> That's not true in a modular ring
2020-09-20 17:34:41 <c_wraith> Oh, I guess it is. nevermind me!
2020-09-20 17:34:49 <phadej> x * 0 = 0, not x ?
2020-09-20 17:35:14 <Cale> That was another equation that would only be satisfied when x == 0
2020-09-20 17:35:27 <c_wraith> Anyway. The real point is that a value of an unknown type with a Num instance is very low.
2020-09-20 17:35:28 <Cale> (again, a fun thing to check holds in any ring)
2020-09-20 17:35:37 <hyperisco> I guess you can use this to dynamically determine which laws might hold
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2020-09-20 17:35:56 <c_wraith> If you add in Eq, you can do that
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