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| 2025-02-11 19:42:01 +0100 | Guest93 | (~Guest93@pool-96-250-224-152.nycmny.fios.verizon.net) (Client Quit) |
| 2025-02-11 19:41:21 +0100 | merijn | (~merijn@host-vr.cgnat-g.v4.dfn.nl) (Ping timeout: 248 seconds) |
| 2025-02-11 19:41:18 +0100 | Lord_of_Life_ | Lord_of_Life |
| 2025-02-11 19:41:06 +0100 | Guest93 | (~Guest93@pool-96-250-224-152.nycmny.fios.verizon.net) |
| 2025-02-11 19:40:48 +0100 | Lord_of_Life | (~Lord@user/lord-of-life/x-2819915) (Ping timeout: 252 seconds) |
| 2025-02-11 19:39:54 +0100 | Lord_of_Life_ | (~Lord@user/lord-of-life/x-2819915) Lord_of_Life |
| 2025-02-11 19:37:30 +0100 | <EvanR> | (A -> a, A <- b) |
| 2025-02-11 19:37:09 +0100 | <monochrom> | lambda the ultimate goto. (->) the ultimate instance. |
| 2025-02-11 19:36:40 +0100 | merijn | (~merijn@host-vr.cgnat-g.v4.dfn.nl) merijn |
| 2025-02-11 19:35:58 +0100 | <ncf> | (->) is the canonical example |
| 2025-02-11 19:35:42 +0100 | <euouae> | oh I see. hm.. I'll keep it in mind when I encounter it |
| 2025-02-11 19:34:59 +0100 | <EvanR> | profunctor class is for types which are functor in one parameter and contravariant functor in the other |
| 2025-02-11 19:34:18 +0100 | <euouae> | yes |
| 2025-02-11 19:34:03 +0100 | <EvanR> | do you know what a contravariant functor is |
| 2025-02-11 19:33:41 +0100 | <euouae> | what's a profunctor? |
| 2025-02-11 19:33:34 +0100 | <monochrom> | But I think weakening to functor is impossible. |
| 2025-02-11 19:33:01 +0100 | <monochrom> | perhaps s/pattern/generalization/ |
| 2025-02-11 19:32:41 +0100 | <EvanR> | lol |
| 2025-02-11 19:32:37 +0100 | <tomsmeding> | I'm not sure if a "pattern" is the right way to look at those :P |
| 2025-02-11 19:32:33 +0100 | <monochrom> | Application: Suppose you want a procedure foo such that foo n reads n lines from stdin and return the list of those n lines. Then it is: sequenceA (replicate n getLine) |
| 2025-02-11 19:32:13 +0100 | <EvanR> | haskell hasn't figured this one out yet |
| 2025-02-11 19:31:44 +0100 | <EvanR> | the next in the pattern would be something of the form (Traversable t, Functor f) => t (f a) -> f (t a) |
| 2025-02-11 19:31:30 +0100 | TheCoffeMaker | (~TheCoffeM@user/thecoffemaker) TheCoffeMaker |
| 2025-02-11 19:30:53 +0100 | <monochrom> | OK yeah sequenceA. |
| 2025-02-11 19:30:52 +0100 | <haskellbridge> | <alexfmpe> * only works when there's |
| 2025-02-11 19:30:42 +0100 | <lambdabot> | (Traversable t, Applicative f) => t (f a) -> f (t a) |
| 2025-02-11 19:30:41 +0100 | <EvanR> | :t sequenceA |
| 2025-02-11 19:30:36 +0100 | <lambdabot> | (Traversable t, Monad m) => t (m a) -> m (t a) |
| 2025-02-11 19:30:35 +0100 | <EvanR> | :t sequence |
| 2025-02-11 19:30:30 +0100 | jespada | (~jespada@2800:a4:2230:3e00:3974:82a3:7f20:1404) jespada |
| 2025-02-11 19:29:41 +0100 | <monochrom> | If you accept sequence, then traverse is just sequence and fmap. |
| 2025-02-11 19:29:32 +0100 | <haskellbridge> | <alexfmpe> * suitable combining |
| 2025-02-11 19:29:25 +0100 | JeremyB99 | (~JeremyB99@2607:fb90:d362:29:704c:ca03:6a71:2d6c) (Ping timeout: 268 seconds) |
| 2025-02-11 19:29:22 +0100 | <monochrom> | You can then go ambitious and say "but liftA10 is always 10. can I make it variable length?". Answer: sequence accepts an arbitary list so it's variable length. (The compromise is that we only have homogeneous lists, so the input list has to be homogeneous, whereas liftA10 is OK with 10 different types.) |
| 2025-02-11 19:29:15 +0100 | <haskellbridge> | Traverse is fmap followed by sequence, so it's kind of foldMap with applicative |
| 2025-02-11 19:29:13 +0100 | <haskellbridge> | <alexfmpe> Yeah, I'd say sequence is basically folding with applicative, but with a fold function that preserves the original structure. |
| 2025-02-11 19:27:34 +0100 | <monochrom> | Remember how you can DIY liftA10, liftA11, liftA12 etc by pure and a lot of liftA2? |
| 2025-02-11 19:27:04 +0100 | peterbecich | (~Thunderbi@syn-047-229-123-186.res.spectrum.com) peterbecich |
| 2025-02-11 19:26:52 +0100 | <monochrom> | It may be useful motivate why one would want it. |
| 2025-02-11 19:26:32 +0100 | <monochrom> | If I'm allowed to illustrate sequence instead: sequence [foo, goo, hoo] = liftA2 (:) foo (liftA2 (:) goo (liftA2 (:) hoo (pure []))))) |
| 2025-02-11 19:25:48 +0100 | ljdarj | (~Thunderbi@user/ljdarj) ljdarj |
| 2025-02-11 19:25:40 +0100 | merijn | (~merijn@host-vr.cgnat-g.v4.dfn.nl) (Ping timeout: 252 seconds) |
| 2025-02-11 19:24:48 +0100 | lisbeths | (uid135845@id-135845.lymington.irccloud.com) (Quit: Connection closed for inactivity) |
| 2025-02-11 19:24:18 +0100 | JeremyB99 | (~JeremyB99@2607:fb90:d362:29:704c:ca03:6a71:2d6c) |
| 2025-02-11 19:24:09 +0100 | JeremyB99 | (~JeremyB99@172.59.98.128) (Remote host closed the connection) |
| 2025-02-11 19:23:50 +0100 | TheCoffeMaker | (~TheCoffeM@user/thecoffemaker) (Remote host closed the connection) |
| 2025-02-11 19:23:46 +0100 | <justsomeguy> | Maybe I just have to write it out on paper. |
| 2025-02-11 19:23:32 +0100 | <justsomeguy> | At this point the examples make sense, but I'm not sure how they evaluate. |
| 2025-02-11 19:22:37 +0100 | JeremyB99 | (~JeremyB99@172.59.98.128) |
| 2025-02-11 19:21:46 +0100 | <monochrom> | If it helps: traverse is impure fmap. |