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2020-09-27 01:49:31 → falafel joins (~falafel@cpe-104-172-194-249.socal.res.rr.com)
2020-09-27 01:49:39 × justanotheruser quits (~justanoth@unaffiliated/justanotheruser) (Ping timeout: 272 seconds)
2020-09-27 01:50:58 hackage tasty-mgolden 0.0.2 - Golden testing provider for tasty with muti-line diff output https://hackage.haskell.org/package/tasty-mgolden-0.0.2 (mbj)
2020-09-27 01:51:27 × ryansmccoy quits (~ryansmcco@156.96.151.132) (Ping timeout: 240 seconds)
2020-09-27 01:52:36 → ryansmccoy joins (~ryansmcco@193.37.254.27)
2020-09-27 01:55:07 × acidjnk_new quits (~acidjnk@p200300d0c723788981cc0ce7da3b2720.dip0.t-ipconnect.de) (Ping timeout: 260 seconds)
2020-09-27 01:55:26 × xff0x_ quits (~fox@2001:1a81:5304:1100:600f:1d33:a4fd:a80e) (Ping timeout: 246 seconds)
2020-09-27 01:57:32 × xerox_ quits (~xerox@unaffiliated/xerox) (Ping timeout: 246 seconds)
2020-09-27 01:57:35 → xff0x_ joins (~fox@2001:1a81:533e:8e00:b1b8:25fe:117c:c2a0)
2020-09-27 01:58:53 → xsperry joins (~as@cpe-188-129-91-153.dynamic.amis.hr)
2020-09-27 01:59:38 → mu_ joins (~mu@unaffiliated/mu)
2020-09-27 01:59:47 × Gurkenglas quits (~Gurkengla@unaffiliated/gurkenglas) (Ping timeout: 240 seconds)
2020-09-27 02:02:26 → merijn joins (~merijn@83-160-49-249.ip.xs4all.nl)
2020-09-27 02:03:33 → p0a joins (~user@unaffiliated/p0a)
2020-09-27 02:03:44 <p0a> hello in [(i,j) | i<-[1..3], j<-[1..3], i < j], am I guaranteed the order in which the tuples are ordered in the resulting list?
2020-09-27 02:05:41 <ski> yes
2020-09-27 02:06:23 <ski> > [(i,j) | i <- [1 .. 3],j <- [1 .. 3],i < j]
2020-09-27 02:06:26 <lambdabot> [(1,2),(1,3),(2,3)]
2020-09-27 02:06:33 <ski> > [(i,j) | i <- [1 .. 3],j <- [1 .. j-1]]
2020-09-27 02:06:35 <lambdabot> *Exception: not an integer: j - 1
2020-09-27 02:06:45 <ski> ah, right
2020-09-27 02:06:55 <p0a> that's a typo
2020-09-27 02:06:57 <ski> > [(i,j) | i <- [1 .. 3],j <- [i+1 .. 3]]
2020-09-27 02:06:59 <lambdabot> [(1,2),(1,3),(2,3)]
2020-09-27 02:07:13 <p0a> I see your point
2020-09-27 02:07:15 <ski> > [(i,j) | i <- [1 .. j-1],j <- [1 .. 3]]
2020-09-27 02:07:17 <lambdabot> *Exception: not an integer: j - 1
2020-09-27 02:07:38 <ski> hmpf, that error comes from another `j' that is in scope
2020-09-27 02:07:45 <ski> > let j = () in [(i,j) | i <- [1 .. j-1],j <- [1 .. 3]]
2020-09-27 02:07:47 <lambdabot> error:
2020-09-27 02:07:47 <lambdabot> • Could not deduce (Num ()) arising from the literal ‘1’
2020-09-27 02:07:47 <lambdabot> from the context: (Num b, Enum b)
2020-09-27 02:07:58 × merijn quits (~merijn@83-160-49-249.ip.xs4all.nl) (Ping timeout: 260 seconds)
2020-09-27 02:07:59 × mu_ quits (~mu@unaffiliated/mu) (Read error: Connection reset by peer)
2020-09-27 02:08:20 <ski> anyway, the `j' from `j <- [1 .. 3]' is not in scope in `i <- [1 .. j-1]', so you can't use `j' there
2020-09-27 02:08:44 → mu_ joins (~mu@unaffiliated/mu)
2020-09-27 02:08:49 <p0a> yeah
2020-09-27 02:09:01 <ski> but the `i' from `i <- [1 .. 3]' is in scope in the `j <- [1 .. 3],i < j' part (and the initial `(i,j)') part, so you could replace that generator part by `j <- [i+1 .. 3]'
2020-09-27 02:09:52 <ski> and the order you get for `[(i,j) | i <- [1 .. 3],j <- [1 .. 3]]' is still the same order. `i' is the "outer loop", `j' is the "inner loop" (whose bounds are allowed to depend on the index `i' of the outer loop)
2020-09-27 02:10:45 <ski> or, if you think of this in terms of enumerating cells in a matrix, then `i' is row index, `j' is column index. and different rows are allowed to have different lengths
2020-09-27 02:11:00 <p0a> yeah, right
2020-09-27 02:11:25 <ski> > [[(i,j) | j <- [i+1 .. 3]] | i <- [1 .. 3]]
2020-09-27 02:11:27 <lambdabot> [[(1,2),(1,3)],[(2,3)],[]]
2020-09-27 02:11:33 <ski> > concat [[(i,j) | j <- [i+1 .. 3]] | i <- [1 .. 3]]
2020-09-27 02:11:35 <lambdabot> [(1,2),(1,3),(2,3)]
2020-09-27 02:11:54 <ski> @undo [(i,j) | i <- [1 .. 3],j <- [i+1 .. 3]]
2020-09-27 02:11:55 <lambdabot> concatMap (\ i -> concatMap (\ j -> [(i, j)]) [i + 1 .. 3]) [1 .. 3]
2020-09-27 02:11:59 <p0a> So that's an implementation I guess, eh
2020-09-27 02:12:03 <ski> @undo [(i,j) | i <- [1 .. 3],j <- [i .. 3],i < j]
2020-09-27 02:12:04 <lambdabot> concatMap (\ i -> concatMap (\ j -> if i < j then [(i, j)] else []) [i .. 3]) [1 .. 3]
2020-09-27 02:12:23 <p0a> okay makes sense
2020-09-27 02:13:25 <ski> the `[[(i,j) | j <- [i+1 .. 3]] | i <- [1 .. 3]]' shows what to do, if you wanted a list of lists (each being a row, in the above image), rather than a single list with all pairs in it (the result of `concat' on the list of lists)
2020-09-27 02:14:04 → remexre joins (~nathan@207-153-38-50.fttp.usinternet.com)
2020-09-27 02:14:36 × rcdilorenzo quits (~rcdiloren@cpe-76-182-87-188.nc.res.rr.com) (Quit: rcdilorenzo)
2020-09-27 02:14:42 <p0a> sure
2020-09-27 02:15:02 <p0a> well that's not what I want, but I see how that is superior in the sense that concatMap gives you the other one
2020-09-27 02:15:22 <p0a> it's a forgetful functor!
2020-09-27 02:15:25 p0a runs
2020-09-27 02:15:30 <ski> hm
2020-09-27 02:16:00 <ski> anyway, earlier generators in a list comprehension vary more slowly than later generators
2020-09-27 02:16:25 <p0a> right
2020-09-27 02:17:42 <p0a> thank you!
2020-09-27 02:18:01 <p0a> One more question, it seems that variable name clashes can happen often in Haskell right?
2020-09-27 02:18:01 × mu_ quits (~mu@unaffiliated/mu) (Read error: Connection reset by peer)
2020-09-27 02:18:13 <p0a> Unless everything is qualified, if an import changes in the future, it may clash
2020-09-27 02:18:26 → mu_ joins (~mu@unaffiliated/mu)
2020-09-27 02:18:55 → asan joins (~yan4138@124.78.5.33)
2020-09-27 02:19:19 <monochrom> You can use explicit imports "import M(a, b, c)" to limit it.
2020-09-27 02:20:13 <p0a> That's a good point, thank you
2020-09-27 02:20:24 × mu_ quits (~mu@unaffiliated/mu) (Client Quit)
2020-09-27 02:21:29 → mu_ joins (~mu@unaffiliated/mu)
2020-09-27 02:21:59 <ski> p0a : if there's an ambiguity, it'll tell you, so you can qualify the name by the module name (or alias) that you imported the identifier from
2020-09-27 02:24:31 <ski> (if the ambiguity is between an imported identifier, and an identifier defined at top-level in the current module, then if you import the identifier qualified, then the plain (unqualified) identifier will refer to the one defined in the current module. and i suppose you don't even need to import qualified, if the identifier is locally bound)
2020-09-27 02:27:05 × lagothrix quits (~lagothrix@unaffiliated/lagothrix) (Killed (card.freenode.net (Nickname regained by services)))
2020-09-27 02:27:13 → lagothrix joins (~lagothrix@unaffiliated/lagothrix)
2020-09-27 02:27:41 → wei2912 joins (~wei2912@unaffiliated/wei2912)
2020-09-27 02:28:39 × mu_ quits (~mu@unaffiliated/mu) (Read error: Connection reset by peer)
2020-09-27 02:28:47 × machinedgod quits (~machinedg@24.105.81.50) (Ping timeout: 240 seconds)
2020-09-27 02:28:47 × danso quits (~dan@107-190-41-58.cpe.teksavvy.com) (Read error: Connection reset by peer)
2020-09-27 02:28:49 → mu__ joins (~mu@unaffiliated/mu)
2020-09-27 02:29:51 → danso joins (~dan@107-190-41-58.cpe.teksavvy.com)
2020-09-27 02:31:40 holo1 is now known as Faye
2020-09-27 02:32:43 × cr3 quits (~cr3@192-222-143-195.qc.cable.ebox.net) (Quit: leaving)
2020-09-27 02:34:12 × nbloomf quits (~nbloomf@2600:1700:83e0:1f40:cc55:612b:5adc:f6f1) (Quit: My MacBook has gone to sleep. ZZZzzz…)
2020-09-27 02:34:20 → xerox_ joins (~xerox@unaffiliated/xerox)
2020-09-27 02:35:15 → thir joins (~thir@p200300f27f0fc60094e773283d7bf825.dip0.t-ipconnect.de)
2020-09-27 02:37:45 × elliott_ quits (~elliott@pool-100-36-54-163.washdc.fios.verizon.net) (Ping timeout: 258 seconds)
2020-09-27 02:38:19 → elliott_ joins (~elliott_@pool-100-36-54-163.washdc.fios.verizon.net)
2020-09-27 02:38:20 × mu__ quits (~mu@unaffiliated/mu) (Read error: Connection reset by peer)
2020-09-27 02:38:48 → mu_ joins (~mu@unaffiliated/mu)
2020-09-27 02:40:15 → merijn joins (~merijn@83-160-49-249.ip.xs4all.nl)
2020-09-27 02:40:19 × thir quits (~thir@p200300f27f0fc60094e773283d7bf825.dip0.t-ipconnect.de) (Ping timeout: 272 seconds)
2020-09-27 02:42:11 × _xor quits (~xor@74.215.46.133) (Ping timeout: 240 seconds)
2020-09-27 02:42:56 → elliott__ joins (~elliott@pool-100-36-54-163.washdc.fios.verizon.net)
2020-09-27 02:44:07 × Achylles quits (~Achylles@200-161-190-140.dsl.telesp.net.br) (Ping timeout: 240 seconds)
2020-09-27 02:48:17 × mu_ quits (~mu@unaffiliated/mu) (Read error: Connection reset by peer)
2020-09-27 02:48:56 → mu_ joins (~mu@unaffiliated/mu)
2020-09-27 02:49:08 <p0a> For example I am trying to use `sum'
2020-09-27 02:49:24 <p0a> but it is defined in Numeric.Matrix. But that is a hidden module?
2020-09-27 02:49:57 hackage mtsl 0.1.0.0 - Reified monad transformer stacks https://hackage.haskell.org/package/mtsl-0.1.0.0 (sgschlesinger)
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