Home freenode/#haskell: Logs Calendar

Logs: freenode/#haskell

←Prev  Next→
Page 1 .. 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 .. 5022
— 502,152 events total
2020-11-22 01:18:08 → conal joins (~conal@198.8.81.205)
2020-11-22 01:19:22 × Tuplanolla quits (~Tuplanoll@91-159-68-239.elisa-laajakaista.fi) (Quit: Leaving.)
2020-11-22 01:22:51 × alp quits (~alp@2a01:e0a:58b:4920:1cfa:109c:d72:5dd) (Ping timeout: 272 seconds)
2020-11-22 01:24:17 → Fractalis joins (~Fractalis@2601:987:280:8d40:eda9:f9e1:2072:cea7)
2020-11-22 01:24:22 × _linker_ quits (~linker@185.12.21.77) (Remote host closed the connection)
2020-11-22 01:31:42 × tmciver quits (~tmciver@cpe-172-101-40-226.maine.res.rr.com) (Read error: Connection reset by peer)
2020-11-22 01:31:51 → justanotheruser joins (~justanoth@unaffiliated/justanotheruser)
2020-11-22 01:33:46 → merijn joins (~merijn@83-160-49-249.ip.xs4all.nl)
2020-11-22 01:34:56 × lucasb quits (uid333435@gateway/web/irccloud.com/x-ssbbedmexymeqbgx) (Quit: Connection closed for inactivity)
2020-11-22 01:35:14 → Lord_of_Life_ joins (~Lord@46.217.221.152)
2020-11-22 01:36:29 × Lord_of_Life quits (~Lord@unaffiliated/lord-of-life/x-0885362) (Ping timeout: 260 seconds)
2020-11-22 01:39:23 × merijn quits (~merijn@83-160-49-249.ip.xs4all.nl) (Ping timeout: 265 seconds)
2020-11-22 01:39:35 → wei2912 joins (~wei2912@unaffiliated/wei2912)
2020-11-22 01:39:51 × conal quits (~conal@198.8.81.205) (Quit: Computer has gone to sleep.)
2020-11-22 01:49:21 × DTZUZU quits (~DTZUZU@207.81.171.116) (Read error: Connection reset by peer)
2020-11-22 01:50:56 <conjunctive> Hi, how do I go about building documentation for all of my dependencies with cabal? I've set Documentation to true for my global cabal config, but :doc still isn't working for third-party packages in GHCI.
2020-11-22 01:51:31 → DTZUZU joins (~DTZUZU@207.81.171.116)
2020-11-22 01:51:58 × da39a3ee5e6b4b0d quits (~da39a3ee5@2403:6200:8876:6c06:8500:38e7:4522:4d5) (Quit: My MacBook has gone to sleep. ZZZzzz…)
2020-11-22 01:54:01 → redmp joins (~redmp@mobile-166-137-178-152.mycingular.net)
2020-11-22 01:57:55 × olligobber quits (olligobber@gateway/vpn/privateinternetaccess/olligobber) (Remote host closed the connection)
2020-11-22 02:03:33 × mupf quits (~micha@v22017094964653601.ultrasrv.de) (Ping timeout: 265 seconds)
2020-11-22 02:05:57 → futuba joins (2fe3e53b@047-227-229-059.res.spectrum.com)
2020-11-22 02:06:20 <futuba> Hi! I am doing CS194 exercise 2 here: https://www.seas.upenn.edu/~cis194/fall16/hw/08-functor-applicative.html
2020-11-22 02:06:29 <futuba> Would somebody be able to walk me through how you would go through func2?
2020-11-22 02:08:57 × xsperry quits (~as@unaffiliated/xsperry) (Remote host closed the connection)
2020-11-22 02:10:05 × redmp quits (~redmp@mobile-166-137-178-152.mycingular.net) (Ping timeout: 260 seconds)
2020-11-22 02:13:54 → merijn joins (~merijn@83-160-49-249.ip.xs4all.nl)
2020-11-22 02:15:54 × jedai42 quits (~jedai@lfbn-dij-1-708-251.w90-100.abo.wanadoo.fr) (Ping timeout: 256 seconds)
2020-11-22 02:19:18 × merijn quits (~merijn@83-160-49-249.ip.xs4all.nl) (Ping timeout: 256 seconds)
2020-11-22 02:23:18 × avoandmayo quits (~textual@122-58-109-105-adsl.sparkbb.co.nz) (Quit: My MacBook has gone to sleep. ZZZzzz…)
2020-11-22 02:26:49 → cr3 joins (~cr3@192-222-143-195.qc.cable.ebox.net)
2020-11-22 02:30:23 → mupf joins (~micha@v22017094964653601.ultrasrv.de)
2020-11-22 02:31:18 × sand_dull quits (~theuser@c-73-149-95-105.hsd1.ct.comcast.net) (Quit: Lost terminal)
2020-11-22 02:31:59 <koz_> futuba: What do you mean by 'how would you go through func2'?
2020-11-22 02:32:23 <futuba> to simplify it as an applicative or functor instance?
2020-11-22 02:32:40 <futuba> the task is to take func2 xs = xs >>= (\x -> xs >>= \y -> return (x,y)), and rewrite it without monad bind
2020-11-22 02:32:45 <koz_> futuba: That's tantamount to straight-up asking for an answer.
2020-11-22 02:32:51 <futuba> i'm not sure how to approach it
2020-11-22 02:33:03 <koz_> OK, so let's think about it this way.
2020-11-22 02:33:03 <futuba> well the answer is here: https://www.seas.upenn.edu/~cis194/fall16/sols/08-functor-applicative.hs
2020-11-22 02:33:11 <futuba> but i'm not sure how i would go about getting there
2020-11-22 02:33:16 <koz_> Suppose instead of a (Monad f) constraint, you had (Functor f)
2020-11-22 02:33:20 <futuba> right
2020-11-22 02:33:29 <koz_> Now, this meand you've only got fmap to work with.
2020-11-22 02:33:34 <futuba> yep
2020-11-22 02:33:45 <koz_> And you have an 'f a', and you gotta get an 'f (a, a)'.
2020-11-22 02:33:50 <futuba> yeah
2020-11-22 02:33:55 <koz_> Now, the only thing you can use is fmap.
2020-11-22 02:34:07 <koz_> So suppose we were to write 'func2 xs = fmap _ xs'.
2020-11-22 02:34:11 <koz_> What type does the hole have?
2020-11-22 02:35:23 <futuba> so fmap is a->b->(f a->f b)
2020-11-22 02:35:35 <futuba> and func2 is f a -> f (a, a)
2020-11-22 02:36:14 <futuba> is that possible?
2020-11-22 02:36:24 <koz_> What do you mean?
2020-11-22 02:36:38 <futuba> oh, i guess you can do a -> (a, a)
2020-11-22 02:36:40 <koz_> You have 'func2 :: (Functor f) => f a -> f (a, a)'
2020-11-22 02:36:48 <koz_> And we've got 'func2 xs = fmap _ xs'.
2020-11-22 02:36:51 <koz_> What type is the hole?
2020-11-22 02:36:57 <futuba> yeah, a->(a, a) should work
2020-11-22 02:37:04 <koz_> OK, can you write such a function?
2020-11-22 02:37:07 × xff0x quits (~fox@2001:1a81:53c2:b800:5bdf:9233:5c1b:206) (Ping timeout: 260 seconds)
2020-11-22 02:37:13 <futuba> \x->(x, x)
2020-11-22 02:37:28 <koz_> So that's the approach.
2020-11-22 02:37:33 <futuba> but that's not correct
2020-11-22 02:37:40 <koz_> Why not?
2020-11-22 02:37:50 <futuba> func2 is not equivalent to fmap \x->(x, x) xs
2020-11-22 02:37:59 <futuba> func1 is equivalent to that
2020-11-22 02:38:28 × fimp quits (~fimp@217.151.98.168) (Remote host closed the connection)
2020-11-22 02:38:30 <futuba> func2 [1,2] gives you [(1,1),(1,2),(2,1),(2,2)]
2020-11-22 02:38:39 → xff0x joins (~fox@2001:1a81:53fc:6700:5177:b787:c6a7:ad81)
2020-11-22 02:38:40 <futuba> it's right for the Just monad
2020-11-22 02:38:43 <futuba> *Maybe
2020-11-22 02:39:00 <koz_> So what does this tell you?
2020-11-22 02:39:04 <koz_> Is Functor enough?
2020-11-22 02:39:14 <futuba> no
2020-11-22 02:39:27 <koz_> OK, so now let's try Applicative. This gives us two new tools to play with.
2020-11-22 02:39:32 <koz_> Which are pure and <*>.
2020-11-22 02:39:50 <koz_> And see if that gets you anyplace.
2020-11-22 02:40:15 <koz_> There's not much I can do beyond saying 'consider your tools carefully and try things' which wouldn't just straight-up give you the answer.
2020-11-22 02:40:45 <futuba> right, like when I read the answer i understood why it works, but i don't know how to get from that to the answer
2020-11-22 02:41:07 <koz_> Yeah, which is why I'm telling you there's no magic formula.
2020-11-22 02:41:15 <futuba> oh
2020-11-22 02:41:18 <koz_> Do you see what func2 is doing in an abstract sense.
2020-11-22 02:41:19 <koz_> ?*
2020-11-22 02:41:19 <lambdabot> Maybe you meant: v @ ? .
2020-11-22 02:41:43 <koz_> To make it easier, consider func2 specialized to Maybe.
2020-11-22 02:41:50 <futuba> yeah, so I was trying that
2020-11-22 02:41:53 <koz_> What's actually being done here?
2020-11-22 02:41:58 <futuba> and func1 func2 and func3 were all identical
2020-11-22 02:42:06 <koz_> Yeah, but that's in terms of _results_.
2020-11-22 02:42:09 <koz_> I wasn't asking for that.
2020-11-22 02:42:25 <koz_> They do very different things, it just so happens that they have the same result if f ~ Maybe.
2020-11-22 02:42:33 <futuba> oh
2020-11-22 02:42:34 <monochrom> No way func1, func2, func3 are the same.
2020-11-22 02:43:25 × darjeeling_ quits (~darjeelin@122.245.219.209) (Ping timeout: 264 seconds)
2020-11-22 02:43:33 <futuba> yeah, i guess i am having a little trouble understanding what func2 is doing abstractly
2020-11-22 02:43:35 → cads joins (~cads@ip-64-72-99-232.lasvegas.net)
2020-11-22 02:44:02 <futuba> it's like unwrapping it twice and then making a pair out of it kind of?
2020-11-22 02:44:04 <monochrom> There is no need to stay abstract. Use f=[] to find out.
2020-11-22 02:44:36 <koz_> (in fact, you already did, and your example of 'func2 [1,2]' holds all the answers you need)
←Prev  Next→
Page 1 .. 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 .. 5022

All times are in UTC.