Home freenode/#haskell: Logs Calendar

Logs: freenode/#haskell

←Prev  Next→
Page 1 .. 758 759 760 761 762 763 764 765 766 767 768 .. 5022
— 502,152 events total
2020-10-20 18:48:30 → GyroW joins (~GyroW@d54C03E98.access.telenet.be)
2020-10-20 18:48:30 × GyroW quits (~GyroW@d54C03E98.access.telenet.be) (Changing host)
2020-10-20 18:48:30 → GyroW joins (~GyroW@unaffiliated/gyrow)
2020-10-20 18:49:35 <ski> so you define `f =< g' to mean `forall y. (exists x. f x = y) => (exists x. g x = y)' ?
2020-10-20 18:52:25 × djellemah quits (~djellemah@2601:5c2:100:96c:e008:b638:39fe:6a54) (Quit: Leaving)
2020-10-20 18:53:17 × shafox quits (~shafox@106.51.234.111) (Remote host closed the connection)
2020-10-20 18:55:16 <frdg> ski: You mean `=<` as less or equal right?
2020-10-20 18:55:41 → heatsink joins (~heatsink@107-136-5-69.lightspeed.sntcca.sbcglobal.net)
2020-10-20 18:56:34 × invaser quits (~Thunderbi@31.148.23.125) (Ping timeout: 272 seconds)
2020-10-20 18:56:45 × GyroW quits (~GyroW@unaffiliated/gyrow) (Ping timeout: 240 seconds)
2020-10-20 18:56:54 → GyroW_ joins (~GyroW@ptr-48ujrfd1ztq5fjywfw3.18120a2.ip6.access.telenet.be)
2020-10-20 18:56:54 × GyroW_ quits (~GyroW@ptr-48ujrfd1ztq5fjywfw3.18120a2.ip6.access.telenet.be) (Changing host)
2020-10-20 18:56:54 → GyroW_ joins (~GyroW@unaffiliated/gyrow)
2020-10-20 18:58:28 hackage parsek 1.0.3.0 - Parallel Parsing Processes https://hackage.haskell.org/package/parsek-1.0.3.0 (JeanPhilippeBernardy)
2020-10-20 18:58:34 <frdg> ski: to me this definition would be for equality of functions.
2020-10-20 18:59:50 <merijn> hmm
2020-10-20 18:59:59 <merijn> Why is there no foldMapM? :\
2020-10-20 19:01:30 <kuribas> foldTraverse?
2020-10-20 19:01:41 <monochrom> Since M is involved, order matters now. Should foldMapM mean left to right? right to left? top down? bottom up?
2020-10-20 19:01:56 <merijn> monochrom: eh
2020-10-20 19:02:07 <merijn> monochrom: That matters for monoids too
2020-10-20 19:02:17 <merijn> monochrom: So that's a bit of a non argument
2020-10-20 19:02:28 × babygnu quits (~robert@gateway/tor-sasl/babygnu) (Remote host closed the connection)
2020-10-20 19:02:40 <kuribas> left to right
2020-10-20 19:02:55 → babygnu joins (~robert@gateway/tor-sasl/babygnu)
2020-10-20 19:03:03 <merijn> monochrom: Exhibit A: Alt
2020-10-20 19:03:31 → berberman_ joins (~berberman@unaffiliated/berberman)
2020-10-20 19:04:00 <phadej> :t Control.MOnad.foldM
2020-10-20 19:04:02 <lambdabot> error:
2020-10-20 19:04:02 × berberman quits (~berberman@unaffiliated/berberman) (Ping timeout: 260 seconds)
2020-10-20 19:04:03 <lambdabot> Not in scope: ‘Control.MOnad.foldM’
2020-10-20 19:04:03 <lambdabot> Perhaps you meant one of these:
2020-10-20 19:04:05 <phadej> :t Control.Monad.foldM
2020-10-20 19:04:07 <lambdabot> (Foldable t, Monad m) => (b -> a -> m b) -> b -> t a -> m b
2020-10-20 19:04:19 <merijn> monochrom: Perhaps you were thinking of commutative monoids? :p
2020-10-20 19:04:27 <monochrom> No.
2020-10-20 19:04:27 → britva joins (~britva@31-10-157-156.cgn.dynamic.upc.ch)
2020-10-20 19:04:38 <merijn> phadej: Yeah, but then I need to write an awkward wrapper :\
2020-10-20 19:04:45 <phadej> (a <> b) <> c = a <> (b <> c)
2020-10-20 19:04:59 <phadej> if <> would "print" something, these will sequence effects in different order
2020-10-20 19:05:27 hackage parsek 1.0.4.0 - Parallel Parsing Processes https://hackage.haskell.org/package/parsek-1.0.4.0 (JeanPhilippeBernardy)
2020-10-20 19:05:29 <phadej> but if you don't care, then foldMapM would just work
2020-10-20 19:05:55 × taurux quits (~taurux@net-130-25-120-210.cust.vodafonedsl.it) (Ping timeout: 265 seconds)
2020-10-20 19:06:12 <phadej> looks like rio and relude define foldMapM
2020-10-20 19:06:16 <merijn> phadej: But that doesn't hold for "(Monad m, Monoid r) => (a -> m r) -> [a] -> m r"
2020-10-20 19:06:26 <merijn> phadej: <> can't have an effect there
2020-10-20 19:06:40 <merijn> phadej: That's just Alt/liftA2 (<>)
2020-10-20 19:06:41 <monochrom> Data.Foldable.foldlM and foldrM
2020-10-20 19:06:47 × leah2 quits (~leah@vuxu.org) (Ping timeout: 244 seconds)
2020-10-20 19:06:47 → taurux joins (~taurux@net-93-146-7-193.cust.vodafonedsl.it)
2020-10-20 19:06:53 <phadej> merijn: there you can still can traverse in arbitrary order
2020-10-20 19:06:55 <merijn> both of which have perfectly well defined semantics
2020-10-20 19:06:55 → tnm joins (~tnm@dslb-084-056-234-071.084.056.pools.vodafone-ip.de)
2020-10-20 19:06:59 <phadej> but I guess you'd expect `traverse` order
2020-10-20 19:07:05 <merijn> phadej: Yes, but the traversal order also impacts the monoid
2020-10-20 19:07:20 → ensyde joins (~ensyde@2600:1702:2e30:1a40:c919:4da8:ba88:82fd)
2020-10-20 19:07:31 <merijn> The order of traversal matters for foldMap *anyway*
2020-10-20 19:07:41 <phadej> :t \f -> fmap fold . traverse f
2020-10-20 19:07:43 <lambdabot> (Monoid b, Traversable t, Applicative f) => (a -> f b) -> t a -> f b
2020-10-20 19:07:44 <merijn> So the fact that it matters for foldMapM is trivial
2020-10-20 19:07:50 <merijn> Of course it does
2020-10-20 19:07:50 <monochrom> Not that order. The other order.
2020-10-20 19:08:16 <phadej> fmapTraverse should be a member of `Traversable`
2020-10-20 19:08:25 <phadej> \f g -> fmap f . traverse g
2020-10-20 19:08:26 <phadej> :t \f g -> fmap f . traverse g
2020-10-20 19:08:27 hackage flashblast 0.0.4.0 - Generate language learning flashcards from video. https://hackage.haskell.org/package/flashblast-0.0.4.0 (locallycompact)
2020-10-20 19:08:28 <lambdabot> (Traversable t, Applicative f) => (t b1 -> b2) -> (a -> f b1) -> t a -> f b2
2020-10-20 19:08:37 × elliott__ quits (~elliott@pool-108-51-141-12.washdc.fios.verizon.net) (Ping timeout: 264 seconds)
2020-10-20 19:09:17 × knupfer quits (~Thunderbi@200116b82c27b200ad7c9ffd9ebcfe8b.dip.versatel-1u1.de) (Ping timeout: 260 seconds)
2020-10-20 19:09:18 <merijn> monochrom: Please show me how the traversal order "doesn't matter" for "Just . First" :)
2020-10-20 19:10:04 <phadej> it doesn't matter, Maybe is commutative effect
2020-10-20 19:10:22 <merijn> phadej: eh, it does...
2020-10-20 19:10:28 <merijn> phadej: You get a different value
2020-10-20 19:10:42 <phadej> you don't
2020-10-20 19:11:10 <monochrom> evaluation order and confluence, vs execution order and effects?
2020-10-20 19:11:13 <phadej> yes
2020-10-20 19:11:19 <monochrom> Must I spell it out?
2020-10-20 19:11:29 <phadej> no, let's just stop
2020-10-20 19:11:41 <phadej> \f -> fmap fold . traverse f -- is what merijn wants
2020-10-20 19:11:56 <merijn> Given a datatype "Foo a" the result of both foldMap and hypothetical foldMapM is dependent on the traversal order of Foo, yes or no?
2020-10-20 19:12:12 × ensyde quits (~ensyde@2600:1702:2e30:1a40:c919:4da8:ba88:82fd) (Ping timeout: 260 seconds)
2020-10-20 19:12:25 <phadej> https://gitlab.haskell.org/ghc/ghc/-/issues/13153 looks like I'm not the only one who wants mapTraverse
2020-10-20 19:13:06 <phadej> merijn: ...
2020-10-20 19:13:41 × conal_ quits (~conal@66.115.157.40) (Quit: Computer has gone to sleep.)
2020-10-20 19:14:15 × tnm quits (~tnm@dslb-084-056-234-071.084.056.pools.vodafone-ip.de) (Quit: leaving)
2020-10-20 19:14:17 <phadej> monochrom meant that if "Foo" is a tree, foldMap can reassosiate the <>, and that shouldn't matter for the end result
2020-10-20 19:14:40 <phadej> as in, foldMap implementation may use associativity of <> to its advantage
2020-10-20 19:14:44 <merijn> phadej: Well my type only admits the Alt monoid in which case it *doesn't* matter
2020-10-20 19:15:00 <phadej> but that's different "order" then traverse-ing
2020-10-20 19:15:21 → tnm joins (~tnm@dslb-084-056-234-071.084.056.pools.vodafone-ip.de)
2020-10-20 19:15:34 × bartemius quits (~bartemius@109.252.19.142) (Remote host closed the connection)
2020-10-20 19:15:39 <merijn> phadej: I'm trying to determine where the asssumptions diverge that leads to monochrom disagreeing.
2020-10-20 19:15:55 <merijn> afaict the type I want only admits the Alt implementation in which case reassociating <> is irrelevant
2020-10-20 19:15:59 <phadej> internet, where people disagree just because
2020-10-20 19:16:19 <merijn> (well, that's a lie I guess it also admits the dual of Alt)
2020-10-20 19:16:40 <merijn> Either way, reassociating of <> doesn't affect the result, effects or no
2020-10-20 19:16:57 × britva quits (~britva@31-10-157-156.cgn.dynamic.upc.ch) (Quit: This computer has gone to sleep)
2020-10-20 19:17:38 <monochrom> So you don't need a general polymorphic function that covers all Foldable instances.
2020-10-20 19:17:40 <merijn> So only the traversal order has an impact on the behaviour of effects, but that has effect on <> anyway
2020-10-20 19:18:28 → conal joins (~conal@64.71.133.70)
←Prev  Next→
Page 1 .. 758 759 760 761 762 763 764 765 766 767 768 .. 5022

All times are in UTC.