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2020-10-21 11:36:08 <ski> so e.g. `take :: Int -> [a] -> [a]' really means `take :: Int -> ([a] -> [a])', and `take 3 "abcdefgh"' really means `(take 3) "abcdefgh"'
2020-10-21 11:36:14 <ski> doesn't matter
2020-10-21 11:36:27 <ski> > take 3 "abcdefgh"
2020-10-21 11:36:29 <lambdabot> "abc"
2020-10-21 11:36:35 <ski> > map (take 3) (tails "abcdefgh")
2020-10-21 11:36:38 <lambdabot> ["abc","bcd","cde","def","efg","fgh","gh","h",""]
2020-10-21 11:36:45 → machinedgod joins (~machinedg@24.105.81.50)
2020-10-21 11:37:16 <ski> `take 3' is a function that, when given a list as input, will give the list of the first three elements of that list (or less, if there wasn't three elements available)
2020-10-21 11:37:16 <nicknick> If we apply some (but not all)of the arguments to a function, what kind of function do we get as a result? ONE WORD ANSWER?
2020-10-21 11:37:39 <nicknick> what kind of function?
2020-10-21 11:38:12 → heatsink joins (~heatsink@107-136-5-69.lightspeed.sntcca.sbcglobal.net)
2020-10-21 11:38:22 <ski> one sometimes says that one gets a "partially applied" function. but that's not a property of the function itself, but rather of the way one arrived at it
2020-10-21 11:39:38 <ski> > elem 'c' "abcd"
2020-10-21 11:39:40 <lambdabot> True
2020-10-21 11:39:42 <ski> > elem 'e' "abcd"
2020-10-21 11:39:45 <lambdabot> False
2020-10-21 11:40:08 <ski> @let elemAbcd x = elem x "abcd"
2020-10-21 11:40:09 <lambdabot> Defined.
2020-10-21 11:40:16 <ski> > elemAbcd 'b'
2020-10-21 11:40:19 <lambdabot> True
2020-10-21 11:40:33 <ski> one could claim that `elemAbcd' is a partial application of `elem'
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2020-10-21 12:09:15 → ixlun joins (~matthew@213.205.241.94)
2020-10-21 12:10:26 <ixlun> Hi all, I was wondering if anyone knew of a way of making an equivalent of swapMVar, swapMVar_ :: MVar a -> a -> IO ()
2020-10-21 12:10:37 <ixlun> I tried `void . swapMVar'
2020-10-21 12:10:58 <ixlun> but that ends up somehow getting rid of the IO monad
2020-10-21 12:11:10 <ixlun> :t void . swapMVar
2020-10-21 12:11:11 <lambdabot> error:
2020-10-21 12:11:11 <lambdabot> Variable not in scope: swapMVar :: a -> f a0
2020-10-21 12:11:15 <merijn> ixlun: Yes, because swapMVar takes two arguments, not 1
2020-10-21 12:11:25 → nicknick joins (75d746c7@117.215.70.199)
2020-10-21 12:11:28 <[exa]> ixlun: you need the magical (.).(.) operator
2020-10-21 12:11:32 <merijn> ixlun: So it's inferring that you're using the Monad instance of functions
2020-10-21 12:11:40 → iMonad joins (1bf6c255@27-246-194-85.adsl.fetnet.net)
2020-10-21 12:11:46 <nicknick> I need an explanation for a0 n xs = foldr (^) n xs
2020-10-21 12:11:48 <merijn> or just, you know, using a variable name
2020-10-21 12:12:07 <[exa]> merijn: so pointful
2020-10-21 12:12:17 <merijn> nicknick: You should probably start by saying where you get confused :)
2020-10-21 12:12:24 <nicknick> What is a0 n xs = foldr (^) n xs doing?
2020-10-21 12:12:50 <ski> @type ((() <$) .) . Control.Concurrent.MVar.swapMVar
2020-10-21 12:12:51 <lambdabot> GHC.MVar.MVar b -> b -> IO ()
2020-10-21 12:13:13 <ixlun> merijn: What's the magical operator you mention above? I can't seem to hoogle that one
2020-10-21 12:13:32 <nicknick> Please tell me: What is a0 n xs = foldr (^) n xs doing?
2020-10-21 12:13:42 → raichoo joins (~raichoo@dslb-084-062-114-218.084.062.pools.vodafone-ip.de)
2020-10-21 12:13:49 <ski> nicknick : `a0 2 [3,4,5] = 3 ^ (4 ^ (5 ^ 2))'
2020-10-21 12:14:16 × random quits (~random@185.219.70.106) (Quit: Leaving)
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2020-10-21 12:14:29 <ski> @let infixr 9 .:; (.:) :: (c0 -> c1) -> (a -> b -> c0) -> (a -> b -> c1); (.:) = (.) . (.)
2020-10-21 12:14:31 <lambdabot> Defined.
2020-10-21 12:14:43 <merijn> ixlun: I didn't mention it and you shouldn't use it, tbh
2020-10-21 12:14:47 <ski> @type (() <$) .: Control.Concurrent.MVar.swapMVar
2020-10-21 12:14:48 <lambdabot> GHC.MVar.MVar b -> b -> IO ()
2020-10-21 12:15:41 <[exa]> ixlun: take a look at type of (.) and compare with (.).(.) (or with the one that ski just defined)
2020-10-21 12:15:50 × coot quits (~coot@37.30.49.255.nat.umts.dynamic.t-mobile.pl) (Ping timeout: 260 seconds)
2020-10-21 12:15:51 coot_ is now known as coot
2020-10-21 12:17:46 <ixlun> :t (.) . (.)
2020-10-21 12:17:47 <lambdabot> (b -> c) -> (a1 -> a2 -> b) -> a1 -> a2 -> c
2020-10-21 12:17:56 → geowiesnot joins (~user@i15-les02-ix2-87-89-181-157.sfr.lns.abo.bbox.fr)
2020-10-21 12:18:13 <iMonad> hi, guys. I have a trouble with monad transformer.
2020-10-21 12:18:23 → karanlikmadde joins (~karanlikm@2a01:c22:b046:2a00:218a:97bb:be49:dab9)
2020-10-21 12:18:34 <iMonad> I am following the wikibook MaybeT example
2020-10-21 12:18:42 <iMonad> newtype MaybeT m a = MaybeT { runMaybeT :: m (Maybe a) }
2020-10-21 12:18:49 → heatsink joins (~heatsink@107-136-5-69.lightspeed.sntcca.sbcglobal.net)
2020-10-21 12:18:57 <iMonad> instance Monad m => Monad (MaybeT m) where return = MaybeT . return . Just
2020-10-21 12:18:59 → coot_ joins (~coot@37.30.51.114.nat.umts.dynamic.t-mobile.pl)
2020-10-21 12:19:12 <iMonad> but it can't compile
2020-10-21 12:19:39 <iMonad> it says
2020-10-21 12:19:40 <iMonad> • Could not deduce (Applicative (MaybeT m)) arising from the superclasses of an instance declaration from the context: Monad m bound by the instance declaration at main.hs:4:10-36 • In the instance declaration for ‘Monad (MaybeT m)’ |4 | instance Monad m => Monad (MaybeT m) where
2020-10-21 12:19:53 <[exa]> iMonad: please pastebin the longer messages
2020-10-21 12:20:13 <ski> you need to make an `Applicative' (and a `Functor') instance, as well
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