Sjoerd Visscher sjoerdvisscher

he/him

sjoerdvisscher / Cofreer.hs

Last active May 3, 2024 10:49

Cofree j-relative comonad

	{-# LANGUAGE RankNTypes #-}
	{-# LANGUAGE PolyKinds #-}
	{-# LANGUAGE GADTs #-}
	{-# LANGUAGE DeriveFunctor #-}
	{-# LANGUAGE StandaloneDeriving #-}
	{-# LANGUAGE MultiParamTypeClasses #-}
	{-# LANGUAGE FlexibleInstances #-}
	module Cofreer where

	import Data.Kind (Type)

sjoerdvisscher / FeedbackMonad.hs

Last active February 22, 2024 13:36

From Lenses to Composable Continuations, and what lies between (Bob Atkey)

	-- https://www.youtube.com/watch?v=YpklMn5yNA0
	{-# LANGUAGE RankNTypes, QuantifiedConstraints #-}
	{-# LANGUAGE UndecidableInstances #-}
	{-# LANGUAGE GADTs #-}
	import Prelude (id, (.), ($), Functor(..), (<$>), fst)
	import Data.Functor.Identity (Identity(..))
	import Data.Void
	import Data.Bifunctor (second)

	class Feedback m where

sjoerdvisscher / diffLinTypes.hs

Last active November 11, 2023 22:45

Deriving differentiation with linear generics

	-- https://twitter.com/paf31/status/1362207106703630338
	{-# LANGUAGE BlockArguments #-}
	{-# LANGUAGE DefaultSignatures #-}
	{-# LANGUAGE DeriveFunctor #-}
	{-# LANGUAGE LinearTypes #-}
	{-# LANGUAGE RankNTypes #-}
	{-# LANGUAGE TypeFamilies #-}
	{-# LANGUAGE TypeOperators #-}
	{-# LANGUAGE FlexibleContexts #-}
	{-# LANGUAGE LambdaCase #-}

sjoerdvisscher / Comonoid.hs

Last active October 15, 2023 09:50

A dual of Applicative

	-- https://github.com/viercc/functor-monad/tree/main/day-comonoid
	{-# LANGUAGE GHC2021 #-}
	import Data.Functor.Day
	import Control.Comonad

	data Multi f a where
	MZ :: a -> Multi f a
	MS :: Multi f (b -> a) -> f b -> Multi f a

	fromMulti :: Applicative f => Multi f a -> f a

sjoerdvisscher / KindCat.hs

Last active October 23, 2023 20:11

Profunctor-based category theory

	{-# LANGUAGE PolyKinds #-}
	{-# LANGUAGE TypeFamilies #-}
	{-# LANGUAGE TypeOperators #-}
	{-# LANGUAGE FlexibleContexts #-}
	{-# LANGUAGE RankNTypes #-}
	{-# LANGUAGE FlexibleInstances #-}
	{-# LANGUAGE StandaloneKindSignatures #-}
	{-# LANGUAGE GADTs #-}
	{-# LANGUAGE UndecidableInstances #-}
	{-# LANGUAGE TypeApplications #-}

sjoerdvisscher / Univ.hs

Last active October 23, 2023 20:10

Universal properties with plain Control.Category

	{-# LANGUAGE PolyKinds #-}
	{-# LANGUAGE TypeFamilies #-}
	{-# LANGUAGE TypeOperators #-}
	{-# LANGUAGE FlexibleContexts #-}
	{-# LANGUAGE MultiParamTypeClasses #-}
	{-# LANGUAGE RankNTypes #-}
	{-# LANGUAGE FlexibleInstances #-}
	{-# LANGUAGE StandaloneKindSignatures #-}
	{-# LANGUAGE GADTs #-}
	{-# LANGUAGE UndecidableInstances #-}

sjoerdvisscher / Object.hs

Last active August 2, 2023 13:09

	{-# LANGUAGE RankNTypes #-}
	import Prelude hiding (id, (.))
	import Control.Category
	import Data.Functor.Coyoneda
	import Data.Bifunctor (first)

	newtype Object f g = Object { runObject :: forall a. f a -> g (Object f g, a) }
	newtype Obj f g = Obj { runObj :: forall a. f a -> Coyoneda g (Obj f g, a) }

	to :: Object f g -> Obj f g

sjoerdvisscher / FixSquares.hs

Last active August 9, 2023 15:39

Folds and unfolds using squares

	-- Using https://hackage.haskell.org/package/squares
	{-# LANGUAGE GADTs #-}
	{-# LANGUAGE TypeFamilies #-}
	{-# LANGUAGE DeriveFunctor #-}
	{-# LANGUAGE DataKinds #-}
	{-# LANGUAGE PolyKinds #-}
	{-# LANGUAGE MultiParamTypeClasses #-}
	{-# LANGUAGE FlexibleInstances #-}
	{-# LANGUAGE RankNTypes #-}
	{-# LANGUAGE ScopedTypeVariables #-}

sjoerdvisscher / ProAlg.hs

Last active July 30, 2023 10:28

Algebra for a profunctor

	{-# LANGUAGE RankNTypes #-}
	{-# LANGUAGE TypeOperators #-}
	{-# LANGUAGE TypeFamilies #-}
	{-# LANGUAGE GADTs #-}
	{-# LANGUAGE FlexibleInstances #-}
	{-# LANGUAGE MultiParamTypeClasses #-}

	import Data.Profunctor
	import Data.Profunctor.Composition
	import Data.Functor.Const

sjoerdvisscher / Rift.hs

Last active October 23, 2023 20:10

All types from the kan-extensions package are special cases of Procompose, Rift and Ran from the profunctors package.

	{-# LANGUAGE StandaloneKindSignatures, GADTs, DataKinds, PolyKinds, RankNTypes, TypeOperators #-}
	module Rift where

	import Data.Bifunctor.Clown
	import Data.Bifunctor.Joker
	import Data.Profunctor
	import Data.Profunctor.Cayley
	import Data.Profunctor.Composition
	import Data.Profunctor.Ran
	import Data.Kind (Type)