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Koji Miyazato viercc

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viercc / coyoneda-dinat.md
Created July 8, 2024 10:47 
type A :: Type
type X :: Type
type F :: Type -> Type
instance Functor F

p :: forall x. (F x, x -> A) -> X

newtype H a = H { runH :: (a -> A) -> X }
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viercc / sequenceA-eq-distribute.md
Last active May 7, 2024 14:46
sequenceA == distribute?

https://twitter.com/lotz84_/status/1787796266484908211

lotz @lotz84_

これを書いていて Vector n a 同士の sequenceA が distribute のように振る舞うのが気になった👀 一般に Traversable の distribute が Distributive の sequenceA に一致することが則を使って言えないだろうか？🤔 QuickCheck で少し探してみたけど反例はなさそう

大枠

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viercc / Isomorphisms2.hs
Created March 5, 2024 10:53
-- Overkilling a cute li'l exercise
-- https://www.reddit.com/r/haskell/comments/v0mfkl/cute_lil_exercise/
{-# LANGUAGE UnicodeSyntax, TypeOperators, ScopedTypeVariables, RankNTypes #-}
{-# LANGUAGE TypeApplications #-}
-- (this time without ImpredicativeTypes, but I'm not sure it's better or not)
module Isomorphisms2(goal, to, from) where
import Prelude hiding (id, (.))
import Control.Category
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viercc / functioncapture.hs
Created February 23, 2024 06:53
-- https://twitter.com/mi12cp/status/1753203763211571656
-- https://twitter.com/rsk0315_h4x/status/1753233137629646938
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ExistentialQuantification #-}
module Main where
import Data.IORef
-- trait Fn()
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viercc / PolymorphicState.hs
Last active December 24, 2023 09:20
{-# LANGUAGE RankNTypes #-}
module PolymorphicState where
{-
-- https://twitter.com/Kory__3/status/1737757423673413635
> forall s, a. Monad (a =>> s -> (s, a)) の値って一意なのでしょうか
-}
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viercc / InfiniteHigherOrderEffect.hs
Last active December 18, 2023 06:37 — forked from ymdryo/SFunctor.hs
{-# LANGUAGE GHC2021 #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE PolyKinds, DataKinds #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE DerivingVia #-}
{-# LANGUAGE UndecidableInstances #-}
module InfiniteHigherOrderEffect where
import Data.Kind (Type)
import Data.Functor.Contravariant (Contravariant)
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viercc / monolocalbinds.hs
Last active December 8, 2023 05:18
Effect of MonoLocalBinds
{-# LANGUAGE ExplicitForAll #-}
-- With MonomorphismRestriction (which is ON by default,)
-- any constrained type variable (e.g. `m` in `Monad m`)
-- are not generalized
{-# LANGUAGE NoMonomorphismRestriction #-}
-- MonoLocalBinds prevents generalization of non-top-level binding
{-# LANGUAGE MonoLocalBinds #-}
-- Compare for
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viercc / type-inference-quirks.md
Last active December 8, 2023 04:20
aaaaaa

(1)

-- m は暗黙に量化されている
{-
action :: forall m. MonadError OutOfRange m => m Int
-}
action :: MonadError OutOfRange m => m Int
action = undefined
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viercc / Check.hs
Last active January 30, 2023 13:37
Note on Distributive laws for semialign package
-- This exists so that I haven't made a silly mistake,
-- like typo or type mismatch of expressions surrounding equal sign.
{-# LANGUAGE TypeOperators #-}
module Check where
import Prelude hiding (zip)
import Data.These
import Data.Zip
import Data.Bifunctor
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viercc / derive.hs
Created December 11, 2022 07:19
-- https://www.reddit.com/r/haskell/comments/z9eyu7/monthly_hask_anything_december_2022/izpv48z/
{-# language
DeriveGeneric,
DerivingVia,
StandaloneDeriving,
TypeOperators,
FlexibleInstances,
ScopedTypeVariables,
TypeFamilies,
TypeApplications,