louispan

# install nix (5.5 mins)
curl https://nixos.org/nix/install | sh

# open a new shell to source nix
bash

# query available haskell compilers
nix-env -qaP -A nixpkgs.haskell.compiler [QUERY]

# install ghc (2.5 mins, cached binary)

louispan

{-# LANGUAGE ApplicativeDo #-}
{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses #-}

louispan

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE UndecidableInstances #-}

-- Example of interpreting using polymorphic variant

louispan

{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE TypeApplications #-}

module Main where

import Control.Lens
import Control.Monad.Reader
import Control.Monad.State
import Data.Diverse.Lens
import Data.Semigroup

louispan

import Control.Monad.Morph
import Data.Functor.Identity

-- | This function combines two different monadic effects,
-- where one of the effects is a reader effect and the other is a
-- producing effect.
--
-- This version results in the reader monad's inner effect to be wrapped
-- around the producing effect.
-- This requires the Reader inner effect to be an MFunctor on Identity.

louispan

{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeFamilyDependencies #-}

module Main where

louispan

{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeFamilyDependencies #-}

module Main where

louispan

{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeFamilyDependencies #-}

-- Example of interpreting using continuation monad instead of the free monad.
module Main where

louispan

{-# LANGUAGE UndecidableSuperClasses #-}
-- https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts.html?highlight=undecidablesuperclasses#ghc-flag--XUndecidableSuperClasses
-- from https://hackage.haskell.org/package/constraint-manip-0.1.0.0/docs/src/Control.ConstraintManip.html
-- To emulate a type function, but partially appliable

type MyC a b = (a ~ b)

-- Do
class (a ~ b) => MyC a b
instance (a ~ b) => MyC a b

louispan

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UndecidableInstances #-}

-- https://wiki.haskell.org/GHC/AdvancedOverlap
-- when using closed type family, data kinds, and proxy