viercc

-- Generate (somewhat hard) test cases for ABC070 D
-- https://atcoder.jp/contests/abc070/tasks/abc070_d
module Main (main) where

type Input = (Int, [(Int, Int, Int)], Int, [(Int, Int)])

main :: IO ()
main = do
  writeInputTo "abc070-d-10k-path.txt" (largePathGraph 10000)
  writeInputTo "abc070-d-20k-path.txt" (largePathGraph 20000)

viercc

openpgp4fpr:B2E1DC9AF16599BD2D873A227BABC58075EC4EE6

viercc

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 }

viercc

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

viercc

-- 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

-- 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

{-# 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

{-# 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

{-# 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

(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