Newest at the top
| 2024-05-01 21:54:06 +0200 | <mauke> | 's' can still be arbitrary |
| 2024-05-01 21:53:41 +0200 | <mauke> | newSTRef just links up the STRef with its surrounding context (that is, it forces the two 's' parameters to be the same) |
| 2024-05-01 21:52:13 +0200 | <monochrom> | s/conflicts/confirms/ . The erroneous code is precisely a victim of a rigid s. |
| 2024-05-01 21:50:30 +0200 | <monochrom> | Here is another elementary answer. goo can take that parameter, but don't call runST. goo :: ST s (STRef s [Int]) -> ST s [Int]. Have someone else write "runST (goo x)". |
| 2024-05-01 21:50:12 +0200 | <Guest67> | it. But it turns out that their suggestion works, and I can apply goo to x |
| 2024-05-01 21:50:11 +0200 | <Guest67> | Thanks. That makes sense in a vacuum, but it kind of conflicts with my understand of why newSTRef [1..10] returns something of type ST s (STRef s [Int]) to begin with. I thought the whole point of doing that is that it forces the type variable s to become "rigid", so the variable x is no longer a polymorphic value that works with all choices of |
| 2024-05-01 21:49:58 +0200 | <shapr> | hackage codebase is kinda rough |
| 2024-05-01 21:46:55 +0200 | noumenon | (~noumenon@113.51-175-156.customer.lyse.net) |
| 2024-05-01 21:44:31 +0200 | <mauke> | ^ monochrom's code basically says: "you don't get to choose an s; you must give me a polymorphic value that works with all possible choices of s" |
| 2024-05-01 21:44:29 +0200 | AlexNoo_ | (~AlexNoo@94.233.240.47) (Client Quit) |
| 2024-05-01 21:44:29 +0200 | AlexNoo_ | (~AlexNoo@94.233.240.47) |
| 2024-05-01 21:43:42 +0200 | <monochrom> | I don't have time to further explain the advanced answer if you don't understand it. |
| 2024-05-01 21:43:22 +0200 | <monochrom> | If you want an advanced answer, if you really want goo to take that parameter, then "goo :: (forall s. ST s (STRef s [Int])) -> [Int]" |
| 2024-05-01 21:43:20 +0200 | <mauke> | and that's not valid as an argument to runST |
| 2024-05-01 21:43:00 +0200 | <mauke> | that is, there could be some specific type T and someone could create a value of type ST T (STRef T [Int]) and pass it to goo |
| 2024-05-01 21:42:41 +0200 | <monochrom> | If you want an elementary answer, goo should not take that parameter. |
| 2024-05-01 21:42:06 +0200 | <mauke> | the way goo is declared, the caller of goo gets to choose an 's' |
| 2024-05-01 21:41:36 +0200 | <mauke> | it just passes through whatever s it gets |
| 2024-05-01 21:41:22 +0200 | <mauke> | readSTRef has no special requirements on s |
| 2024-05-01 21:41:11 +0200 | <mauke> | depends |
| 2024-05-01 21:41:07 +0200 | <lambdabot> | STRef s a -> ST s a |
| 2024-05-01 21:41:06 +0200 | <mauke> | :t readSTRef |
| 2024-05-01 21:40:57 +0200 | <Guest67> | Does readSTRef ref not return a value that's fully polymorphic in s? |
| 2024-05-01 21:40:46 +0200 | <mauke> | but goo does not |
| 2024-05-01 21:40:37 +0200 | <mauke> | runST requires its argument to be fully polymorphic in s |
| 2024-05-01 21:40:15 +0200 | <lambdabot> | (forall s. ST s a) -> a |
| 2024-05-01 21:40:14 +0200 | <mauke> | :t runST |
| 2024-05-01 21:39:58 +0200 | <mauke> | goo's type looks sus |
| 2024-05-01 21:38:40 +0200 | <Guest67> | In foo, that's not supposed to be a smiley face, it's supposed to be "(0 : )" |
| 2024-05-01 21:38:16 +0200 | <Guest67> | readSTRef ref |
| 2024-05-01 21:38:16 +0200 | <Guest67> | foo ref |
| 2024-05-01 21:38:15 +0200 | <Guest67> | ref <- x — type error here |
| 2024-05-01 21:38:15 +0200 | <Guest67> | goo x = runST $ do |
| 2024-05-01 21:38:14 +0200 | <Guest67> | goo :: ST s (STRef s [Int]) -> [Int] |
| 2024-05-01 21:38:14 +0200 | <Guest67> | foo ref = modifySTRef ref (0 :) |
| 2024-05-01 21:38:13 +0200 | <Guest67> | foo :: STRef s [Int] -> ST s () |
| 2024-05-01 21:38:13 +0200 | <Guest67> | x = newSTRef $ [1..10] |
| 2024-05-01 21:38:12 +0200 | <Guest67> | x :: ST s (STRef s [Int]) |
| 2024-05-01 21:38:12 +0200 | <Guest67> | Could anyone help me understand why this code doesn’t work/what the correct way of achieving this sort of functionality is? The type error lies with the parameter x in goo, when I left-arrow bind it to ref. |
| 2024-05-01 21:35:41 +0200 | Guest67 | (~Guest67@129.170.197.127) |
| 2024-05-01 21:34:02 +0200 | Batzy | (~quassel@user/batzy) |
| 2024-05-01 21:14:44 +0200 | malte | (~malte@mal.tc) |
| 2024-05-01 21:14:12 +0200 | tessd | (~test@evw199.neoplus.adsl.tpnet.pl) |
| 2024-05-01 21:13:34 +0200 | malte | (~malte@mal.tc) (Remote host closed the connection) |
| 2024-05-01 21:11:00 +0200 | madeleine-sydney | (~madeleine@c-76-155-235-153.hsd1.co.comcast.net) |
| 2024-05-01 21:09:46 +0200 | michalz | (~michalz@185.246.207.200) |
| 2024-05-01 21:09:15 +0200 | emmanuelux | (~emmanuelu@user/emmanuelux) |
| 2024-05-01 21:07:11 +0200 | michalz | (~michalz@185.246.207.218) (Client Quit) |
| 2024-05-01 21:05:43 +0200 | michalz | (~michalz@185.246.207.218) |
| 2024-05-01 21:02:40 +0200 | michalz | (~michalz@185.246.207.218) (Client Quit) |