polysemy VS ghc

Looking for a few projects that make use of it, I found accelerate, hawk, polysemy and pretty-simple, so I'll be interested to poke around in their code and see how they have things set up.

Right, I think I'll just give it a shot to see. Polysemy is nice but I'm still having trouble getting what I want out of it (which may very well be entirely a fault of my own understanding)

Languages such as Koka only support algebraic effects, not scoping operations such as catch and listen. The Effect Handlers in Scope paper introduces scoping operations, which lead to the Haskell libraries fused-effects and polysemy, but they turned out to have some weird semantics. eff is her effort to fix that.

Looking at the interpreter for Reader might give some clues if this doesn't work. https://github.com/polysemy-research/polysemy/blob/master/src/Polysemy/Reader.hs#L38-L45

*But I'm not terribly well versed in Scala's other DI offerings. I came from Haskell and didn't find anything in Scala that clicked with me until I found ZIO. It reminded me a lot of my favorite way of writing Haskell programs (https://github.com/polysemy-research/polysemy)—albeit with a completely different implementation.

Haskell has entered the chat. $ ghci GHCi, version 8.8.4: https://www.haskell.org/ghc/ :? for help Prelude> one = 1::Double Prelude> zero = 0::Double Prelude> :t one/zero one/zero :: Double Prelude> one/zero Infinity

[email protected] % ghci -XNoImplicitPrelude GHCi, version 8.8.4: https://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/bss/.ghc/ghci.conf GHCi> :{ GHCi| data Nat = Z | S Nat GHCi| GHCi| listNat :: a -> Nat -> a -> [a] GHCi| listNat x y z = l y GHCi| where GHCi| l Z = [z] GHCi| l (S p) = x : l p GHCi| :} data Nat = ... listNat :: a -> Nat -> a -> [a] GHCi> listNat 1 (S (S Z)) 3 [1,1,3] (0.00 secs, 71,512 bytes)

GHCi, version 8.4.3: http://www.haskell.org/ghc/ :? for help Prelude> fact x = if x == 1 then 1 else x * (fact (x-1)) Prelude> (fact 100) - (fact 50) 93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976126104193051984542783611150085120442072486358431039488000000000000 Prelude> (fact 101) - (fact 51) 9425947759838359420851623124482936749562312794702543768327889353416977599316221476503087861590257228158336107723325356566900403091540004279983013888000000000000 Prelude> ((fact 101) - (fact 51)) / ((fact 100) - (fact 50)) 100.99999999999999

[email protected] % ghci GHCi, version 8.8.4: https://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/bss/.ghc/ghci.conf GHCi> import Data.Map (0.01 secs, 0 bytes) GHCi> map = fromList [(1,1),(2,3),(5,8)] map :: (Ord k, Num k, Num a) => Map k a (0.04 secs, 24,872 bytes) GHCi> map ! 1 1 it :: Num a => a (0.01 secs, 58,424 bytes) GHCi> map ! 2 3 it :: Num a => a (0.01 secs, 58,424 bytes) GHCi> map ! 3 *** Exception: Map.!: given key is not an element in the map CallStack (from HasCallStack): error, called at libraries/containers/containers/src/Data/Map/Internal.hs:627:17 in containers-0.6.2.1:Data.Map.Internal

% ghci GHCi, version 8.8.4: https://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/bss/.ghc/ghci.conf GHCi> data List a = Nil | Cons a (List a) deriving Show data List a = ... (0.02 secs, 0 bytes) GHCi> :{ GHCi| lengthList :: List a -> Int GHCi| lengthList Nil = 0 GHCi| lengthList (Cons _ xs) = 1 + lengthList xs GHCi| :} lengthList :: List a -> Int (0.00 secs, 0 bytes) GHCi> lengthList Nil 0 it :: Int (0.00 secs, 58,752 bytes) GHCi> lengthList (Cons 'a' Nil) 1 it :: Int (0.00 secs, 57,976 bytes) GHCi> lengthList (Cons 123 Nil) 1 it :: Int (0.00 secs, 57,840 bytes) GHCi> lengthList (Cons 1 (Cons 2 (Cons 3 (Cons 4 (Cons 5 (Cons 6 (Cons 7 (Cons 8 (Cons 9 (Cons 10 Nil)))))))))) 10 it :: Int (0.01 secs, 59,584 bytes)

sh sh> ghci GHCi, version 8.10.7: https://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /your/home/.config/ghc/ghci.conf λ> :l 2022-04-15-Combinations-TailAfterTail'.lhs [1 of 1] Compiling TailAfterTail ( 2022-04-15-Combinations-TailAfterTail'.lhs, interpreted ) Ok, one module loaded. λ> unsafe_allCombinationsWithSingleStep [1..5] [[[[1]],[[2]],[[3]],[[4]],[[5]]],[[[1,2],[1,3],[1,4],[1,5]],[[2,3],[2,4],[2,5]],[[3,4],[3,5]],[[4,5]]],[[[1,2,3],[1,2,4],[1,2,5],[1,3,4],[1,3,5],[1,4,5]],[[2,3,4],[2,3,5],[2,4,5]],[[3,4,5]]],[[[1,2,3,4],[1,2,3,5],[1,2,4,5],[1,3,4,5]],[[2,3,4,5]]],[[[1,2,3,4,5]]],[[]*** Exception: 2022-04-15-Combinations-TailAfterTail'.lhs:(120,9)-(122,52): Non-exhaustive patterns in function genStep

The GHC runtime system including its core interpreter loop and garbage collector are written in C.

The next release of base (4.17) will include the Generically1 newtype which can be used to derive Applicative and I really want to discuss challenges in pushing beyond that.