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2020-10-07 08:45:27 × xff0x_ quits (~fox@2001:1a81:5374:e100:2800:5137:cbd5:b8c6) (Ping timeout: 240 seconds)
2020-10-07 08:45:33 <tomsmeding> 2020, the year in which triples have four elements
2020-10-07 08:46:06 → LKoen joins (~LKoen@81.255.219.130)
2020-10-07 08:46:31 → xff0x_ joins (~fox@2001:1a81:5374:e100:90a4:ed3f:c45e:9759)
2020-10-07 08:47:56 → ixlun joins (~matthew@213.205.241.94)
2020-10-07 08:49:46 × heatsink quits (~heatsink@107-136-5-69.lightspeed.sntcca.sbcglobal.net) (Ping timeout: 272 seconds)
2020-10-07 08:52:15 <maerwald> dminuoso: 3
2020-10-07 08:52:31 <maerwald> "unknown-linux" is one :p
2020-10-07 08:52:37 <kuribas> > length (1, 2, (3, 4))
2020-10-07 08:52:39 <lambdabot> error:
2020-10-07 08:52:39 <lambdabot> • No instance for (Foldable ((,,) Integer Integer))
2020-10-07 08:52:39 <lambdabot> arising from a use of ‘length’
2020-10-07 08:52:47 <kuribas> > length (1, (2, (3, 4)))
2020-10-07 08:52:49 <lambdabot> 1
2020-10-07 08:53:55 × shatriff quits (~vitaliish@217.27.153.240) (Ping timeout: 256 seconds)
2020-10-07 08:55:53 × hnOsmium0001 quits (uid453710@gateway/web/irccloud.com/x-wkoagvlxhlhmtgti) (Quit: Connection closed for inactivity)
2020-10-07 08:56:44 <dminuoso> maerwald: Oh I know. ;)
2020-10-07 08:58:11 <dminuoso> kuribas: There's a debatable `instance Foldable ((,) a)`
2020-10-07 08:58:19 <dminuoso> But it doesn't exist for longer tuples
2020-10-07 08:58:53 <kuribas> :t length
2020-10-07 08:58:54 <lambdabot> Foldable t => t a -> Int
2020-10-07 08:59:32 <dminuoso> The idea is that `(a,)` is a Foldable if we think of it as a 1-element container with some extra baggage. :p
2020-10-07 09:00:29 × ttc quits (tomtauma1@gateway/shell/matrix.org/x-jhgolvjpuztnuiul) (Quit: Idle for 30+ days)
2020-10-07 09:01:13 → thir joins (~thir@p200300f27f0fc60038c1b16891cbfa03.dip0.t-ipconnect.de)
2020-10-07 09:02:03 × wangoe[m] quits (wangoematr@gateway/shell/matrix.org/x-ygktxbgtoupbgdmu) (Quit: Idle for 30+ days)
2020-10-07 09:02:22 ← gcoakes[m] parts (gcoakesmat@gateway/shell/matrix.org/x-klflsytbyxwgnxns) ("Kicked by @appservice-irc:matrix.org : Idle for 30+ days")
2020-10-07 09:02:58 <kuribas> > (1, 2, (3, 4)) ..^ (folded . to length)
2020-10-07 09:03:00 <lambdabot> error:
2020-10-07 09:03:00 <lambdabot> • Variable not in scope:
2020-10-07 09:03:00 <lambdabot> (..^)
2020-10-07 09:03:12 <kuribas> > (1, 2, (3, 4)) ^.. (folded . to length)
2020-10-07 09:03:15 <lambdabot> error:
2020-10-07 09:03:15 <lambdabot> • No instance for (Foldable ((,,) Integer Integer))
2020-10-07 09:03:15 <lambdabot> arising from a use of ‘folded’
2020-10-07 09:03:38 → DavidEichmann joins (~david@43.240.198.146.dyn.plus.net)
2020-10-07 09:03:46 <kuribas> dminuoso: the type system prevents any other instance for tuple.
2020-10-07 09:04:28 <dminuoso> Huh?
2020-10-07 09:04:42 <dminuoso> We can write `instance Foldable ((,,) a b) where ...` just fine
2020-10-07 09:04:54 → ahmr88 joins (~ahmr88@cpc85006-haye22-2-0-cust131.17-4.cable.virginm.net)
2020-10-07 09:05:27 × thir quits (~thir@p200300f27f0fc60038c1b16891cbfa03.dip0.t-ipconnect.de) (Ping timeout: 240 seconds)
2020-10-07 09:05:35 × tsrt^ quits (tsrt@ip98-184-89-2.mc.at.cox.net) ()
2020-10-07 09:06:48 <kuribas> I mean for 2 tuple
2020-10-07 09:07:15 → ffl^ joins (ffl@ip98-184-89-2.mc.at.cox.net)
2020-10-07 09:08:02 <dminuoso> kuribas: Just because it's possible to write an instance, it doesn't make it good.
2020-10-07 09:08:17 <dminuoso> I think the `Foldable ((,) a)` instance shouldn't exist at all
2020-10-07 09:08:26 × mmohammadi981266 quits (~mmohammad@5.238.172.236) (Ping timeout: 256 seconds)
2020-10-07 09:08:44 <dminuoso> It will just type check for the odd `foldMap f g` and very likely do something unexpected.
2020-10-07 09:08:51 <kuribas> it doesn't look that useful.
2020-10-07 09:09:07 × __skn quits (~sunil@sec.nimmagadda.net) (Quit: ZNC 1.7.1 - https://znc.in)
2020-10-07 09:09:31 <dminuoso> I mean if I did `sum (10,20)` I'd naively expect that to yield 30 or not type check.
2020-10-07 09:09:36 <dminuoso> Instead I get `20`
2020-10-07 09:09:45 → todda7 joins (~torstein@athedsl-4367507.home.otenet.gr)
2020-10-07 09:09:47 <dminuoso> Principle of maximum surprise. :)
2020-10-07 09:09:56 <kuribas> dminuoso: but that sum is more polymorphic
2020-10-07 09:10:17 <dminuoso> So?
2020-10-07 09:10:46 <ptrcmd> > sum (10, 20)
2020-10-07 09:10:49 <lambdabot> 20
2020-10-07 09:10:54 <ptrcmd> lol
2020-10-07 09:11:02 <kuribas> how do you sum ("10", 20)?
2020-10-07 09:11:15 × alp quits (~alp@2a01:e0a:58b:4920:18a9:ec9:c879:c1d7) (Remote host closed the connection)
2020-10-07 09:11:34 → alp joins (~alp@2a01:e0a:58b:4920:3027:b807:1b0e:5ebe)
2020-10-07 09:12:18 → __monty__ joins (~toonn@unaffiliated/toonn)
2020-10-07 09:12:25 <dminuoso> It's sort of how `lens` allows you to view through a Traversal.
2020-10-07 09:12:37 <dminuoso> I mean yeah, there's a sensible implementation, but it likely doesn't do what you think it does.
2020-10-07 09:13:19 <dminuoso> % [Product 10, Product 20, Product 30] ^. each
2020-10-07 09:13:19 <yahb> dminuoso: Product {getProduct = 6000}
2020-10-07 09:14:30 <dminuoso> Sometimes leaving out an obvious implementation helps avoid people trip into bugs because the code type checks and does something very unexpected.
2020-10-07 09:15:33 <kuribas> % (Sum 10, Sum 20) ^. each
2020-10-07 09:15:33 <yahb> kuribas: Sum {getSum = 30}
2020-10-07 09:15:53 <dminuoso> If you consider something less obvious like
2020-10-07 09:16:11 × bor0 quits (~boro@unaffiliated/boro/x-000000001) (Quit: Leaving)
2020-10-07 09:16:16 <dminuoso> % [Left 'f', Right 1, Left 'o', Right 2, Left 'o'] ^. each._Left
2020-10-07 09:16:16 <yahb> dminuoso: ; <interactive>:71:53: error:; * No instance for (Monoid Char) arising from a use of `each'; * In the first argument of `(.)', namely `each'; In the second argument of `(^.)', namely `each . _Left'; In the expression: [Left 'f', Right 1, Left 'o', Right 2, ....] ^. each . _Left
2020-10-07 09:16:16 <kuribas> :t each
2020-10-07 09:16:19 <lambdabot> (Each s t a b, Applicative f) => (a -> f b) -> s -> f t
2020-10-07 09:16:37 <dminuoso> But then do something like
2020-10-07 09:16:50 <dminuoso> % [Left "f", Right 1, Left "o", Right 2, Left "o"] ^. (each._Left)
2020-10-07 09:16:50 <yahb> dminuoso: "foo"
2020-10-07 09:17:13 <dminuoso> It's not very obvious what's happening. Especially because `(^.)` doesnt make that obvious
2020-10-07 09:17:33 <dminuoso> (^.) :: s -> Getting a s a -> a
2020-10-07 09:17:37 <dminuoso> type Getting r s a = (a -> Const r a) -> s -> Const r s
2020-10-07 09:17:48 <dminuoso> And then, if you stare at the above Applicative constraint
2020-10-07 09:17:50 <dminuoso> you get
2020-10-07 09:18:00 <dminuoso> instance Monoid m => Applicative (Const m :: Type -> Type)
2020-10-07 09:18:21 <dminuoso> So yeah. Everything works out somehow
2020-10-07 09:18:39 → mmohammadi981266 joins (~mmohammad@5.238.172.236)
2020-10-07 09:19:15 × alp quits (~alp@2a01:e0a:58b:4920:3027:b807:1b0e:5ebe) (Read error: Connection reset by peer)
2020-10-07 09:19:23 <kuribas> lenses leaky abstractions
2020-10-07 09:19:27 <dminuoso> Which is one of the reasons I like optics more
2020-10-07 09:19:33 <dminuoso> optics just flat out fails with a type error on that one
2020-10-07 09:19:35 → alp joins (~alp@2a01:e0a:58b:4920:3027:b807:1b0e:5ebe)
2020-10-07 09:19:40 <dminuoso> And forces you to use a fold explicitly if you wanted that
2020-10-07 09:20:46 → ubert joins (~Thunderbi@2a02:8109:9880:303c:ca5b:76ff:fe29:f233)
2020-10-07 09:24:57 <tomjaguarpaw> I've been bitten by (^.) doing mconcat on the targets. I wish they hadn't supported that (but instead provided a different combinator that does do that. "mconcatOf" would have been fine).
2020-10-07 09:25:38 × bahamas quits (~lucian@unaffiliated/bahamas) (Ping timeout: 260 seconds)
2020-10-07 09:29:35 → shatriff joins (~vitaliish@88.155.140.206)
2020-10-07 09:31:05 × oxide quits (~lambda@unaffiliated/mclaren) (Ping timeout: 240 seconds)
2020-10-07 09:31:49 → seanvert joins (~user@177.84.244.242)
2020-10-07 09:36:00 × GyroW quits (~GyroW@unaffiliated/gyrow) (Ping timeout: 272 seconds)
2020-10-07 09:36:04 → GyroW_ joins (~GyroW@ptr-48ujrfd1ztq5fjywfw3.18120a2.ip6.access.telenet.be)
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