Skip to content

Instantly share code, notes, and snippets.

View viercc's full-sized avatar

Koji Miyazato viercc

13 followers · 8 following
View GitHub Profile
@viercc
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
@viercc
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()
@viercc
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
-}
@viercc
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)
@viercc
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
@viercc
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
@viercc
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
@viercc
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,
@viercc
viercc / Foldl.hs
Last active November 30, 2022 06:00
Performance of manually implemented foldl' on GHCi
module Foldl(foldl', foldl'Copied, foldl'CopiedMono, foldl'Recursion, foldl'Recursion2) where
import Data.List (foldl')
import GHC.Exts (oneShot)
foldl'Copied :: Foldable t => (b -> a -> b) -> b -> t a -> b
{-# INLINE foldl'Copied #-}
foldl'Copied f z0 = \ xs -> foldr (\ (x::a) (k::b->b) -> oneShot (\ (z::b) -> z `seq` k (f z x))) (id::b->b) xs z0
foldl'CopiedMono :: (b -> a -> b) -> b -> [a] -> b
@viercc
viercc / gadt-filter-with-typeable.hs
Created October 27, 2022 08:08
Generalising / DRYing functions which apply to GADTs
{-# LANGUAGE GADTs, DataKinds #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeApplications #-}
module Main where
import Data.Typeable (cast)
import Type.Reflection