LSLeary / Search.hs

Last active July 3, 2025 08:29

Broad search for arbitrary Foldables; a solution to: https://github.com/effectfully-ou/haskell-challenges/tree/master/h9-traversable-search

	{-# LANGUAGE GHC2021, BlockArguments, LambdaCase #-}

	module Search (search) where

	search :: Foldable f => (a -> Bool) -> f a -> Maybe a
	search p = try . foldMap \x -> if p x
	then Succeed x
	else Fail

LSLeary / LambdaEncodings.md

Last active February 18, 2025 22:19

Scott & Church Encodings

Algebraic Data Types

It suffices to describe sums, products and their identities to obtain the full wealth of ADTs:

newtype a + b = Sum{ matchSum :: forall r. (a -> r) -> (b -> r) -> r) }

left :: a -> a + b

LSLeary / fragment.cabal

Created February 12, 2025 00:47

Structuring a cabal file so as to provide a unified `dev` component.

	-- A demonstration, using a fragment of an unpublished library as-is.

	-- Split out fields shared by all components into a common stanza:
	common shared
	build-depends: base
	default-language: Haskell2010
	default-extensions: ImportQualifiedPost
	GeneralisedNewtypeDeriving
	DerivingVia
	DeriveTraversable

LSLeary / EventManager.hs

Created January 21, 2025 16:07

A simple, functional event manager.

	{-# LANGUAGE RankNTypes, PolyKinds, GeneralisedNewtypeDeriving #-}

	module EventManager (
	EventManager,
	EventTag, eventTag,
	attach, trigger,
	) where

	-- base
	import Prelude hiding (lookup)

LSLeary / Coercible.hs

Last active January 5, 2025 10:15

Generalised Coercible

	-- These coercions could probably be generated automatically with a
	-- type class and this plugin:
	-- https://github.com/noughtmare/transitive-constraint-plugin

	{-# LANGUAGE UnboxedTuples, UnliftedNewtypes, ExplicitNamespaces #-}
	{-# LANGUAGE RoleAnnotations, DataKinds, QuantifiedConstraints #-}

	module Coercible (

	Coercible(..),

LSLeary / Yoneda.hs

Last active February 4, 2025 04:00

A more general treatment of the Yoneda lemma than is given in Data.Functor.Yoneda.

	{-# LANGUAGE GHC2021, BlockArguments #-}

	module Yoneda where

	import Prelude hiding (id, (.), map)
	import Control.Category


	-- Preliminaries
	class (Category c, Category d) => ExoFunctor c d f where

LSLeary / Collapse.hs

Last active November 19, 2024 09:08 — forked from VictorTaelin/collapse_monad.hs

A* Collapse Monad (see https://www.reddit.com/r/haskell/comments/1gu476s/the_collapse_monad/lxsyge6/)

	{-# LANGUAGE LambdaCase #-}

	module Collapse where

	-- base
	import Data.Functor ((<&>))
	import Data.Functor.Classes (Show1)
	import Data.Foldable (toList)
	import Control.Monad (ap)

LSLeary / Graded.hs

Last active November 8, 2024 04:36 — forked from axman6/Tracked Exceptions.hs

Checked exceptions implemented by grading IO with the set of exceptions an action may throw.

	{-# LANGUAGE DataKinds, TypeFamilies, UndecidableInstances, RoleAnnotations
	, QuantifiedConstraints, RebindableSyntax, BlockArguments
	, RequiredTypeArguments
	#-}

	module Graded (

	GradedAppl(..), (<>), (<), (*>),
	GradedAlt(..),
	GradedMonad(..), (>>),

LSLeary / 0-InlineFix.hs

Last active October 3, 2024 22:51

Unrolling recursive functions at static arguments using church numerals

LSLeary / LeibnizC.hs

Created September 23, 2024 08:06

Leibniz equality as a quantified constraint with safe reification and reflection

	{-# LANGUAGE QuantifiedConstraints
	, UndecidableInstances
	, AllowAmbiguousTypes
	#-}
	{-# OPTIONS_GHC -Wno-simplifiable-class-constraints #-}

	module LeibnizC where

	import Leibniz

Leary LSLeary