anandabits

// This example shows how higher-kinded types can be emulated in Swift today.
// It acheives correct typing at the cost of some boilerplate, manual lifting and an existential representation.
// The technique below was directly inspired by the paper Lightweight Higher-Kinded Polymorphism
// by Jeremy Yallop and Leo White found at http://ocamllabs.io/higher/lightweight-higher-kinded-polymorphism.pdf

/// `ConstructorTag` represents a type constructor.
/// `Argument` represents an argument to the type constructor.
struct Apply<ConstructorTag, Argument> {
    /// An existential containing a value of `Constructor<Argument>`
    /// Where `Constructor` is the type constructor represented by `ConstructorTag`

LukaJCB

module Algebra where

import Prelude
import Control.Monad.Eff (Eff)
import Data.Maybe (Maybe(..))


newtype ConsoleAlg f = ConsoleAlg
  { printLn :: String -> f Unit 
  , readLn :: f String

hallettj

/*
 * Concept for emulating higher-kinded types using Flow. Instead of passing
 * a type that has not been applied to parameters, this pattern passes
 * a type-level function that will map a parameter type to the desired
 * higher-kinded type applied to the given parameter.
 *
 * @flow
 */

// a higher-kinded type is represented indirectly via a type-level function from

gcanti

// @flow

// type-level dictionary URI -> type constructor
export type URI2HKT<U, L, A> = {
  Identity: Identity<A>
  // other type constructors here...
  // Option: Option<A>,
  // Either: Either<L, A>,
  // Foo: Foo<U, L, A>
}

gcanti

import { Monad, Monad1 } from 'fp-ts/lib/Monad'
import { HKT, URIS, Type } from 'fp-ts/lib/HKT'
import { liftA2 } from 'fp-ts/lib/Apply'
import { flatten } from 'fp-ts/lib/Chain'
import { Newtype, iso } from 'newtype-ts'

// Adapted from https://tech.iheart.com/why-fp-its-the-composition-f585d17b01d3

//
// newtypes

busypeoples

/* 
  Slaying a UI Anti Pattern in ReasonML
  Based on Kris Jenkins original writing.
  http://blog.jenkster.com/2016/06/how-elm-slays-a-ui-antipattern.html
*/
type remoteData 'e 'a =
  | NotAsked
  | Loading
  | Failure 'e
  | Success 'a;

Icelandjack

reddit discussion

IxMonad implies Monad for (EDIT: Exists as LowerIx with newtype LiftIx m i j a = LiftIx (m a))

and `

newtype Same :: (k -> k -> k' -> Type) -> (k -> k' -> Type) where
  Same :: p f f a -> Same p f a

arianvp

import Control.Monad.IO.Class
import Control.Monad.Codensity
import System.IO


managedActions :: Codensity IO ()
managedActions = do
  input <- Codensity $ withFile "in.txt" ReadMode
  output <- Codensity $ withFile "out.txt" WriteMode
  contents <- liftIO $ hGetContents input

paf31

FreeAp f is a Comonad

While thinking about comonads as spaces and Day convolution, I realized an interesting thing. The free applicative functor generated by a comonad f is also a comonad.

The free applicative can be defined in a few different ways, but I like to define it like this:

data FreeApplicative f a = Pure a | Free (Day f (FreeApplicative f) a)

bfncs

This is a port of the RemoteData type from Kris Jenkins article „How Elm Slays a UI Antipattern“ to TypeScript with TsMonad. There have been ports to Flow and JavaScript as well.