MorrowM

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE GADTs #-}
module Shoe where

data ShoeState = Off | Untied | On

data Shoes l r where
  PutOnL :: Shoes Off r -> Shoes Untied r 
  PutOnR :: Shoes l Off -> Shoes l Untied
  TieL   :: Shoes Untied r -> Shoes On r 

MorrowM

Haskell Quickstart Guide (as of September 2021)

Installation

On all platforms

1. Install GHCup, this will manage all of your Haskell development tools. Follow the onscreen instructions. When it asks you if you'd like to install Haskell language server, say yes.
2. Install the Haskell extension for VSCode. This is the front end for the Haskell Language Server (hls). If you'd like to use hls with another editor of your choice (any editor with lsp support), see this section of the hls documentation.

Creating your first Cabal project

MorrowM

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE PatternSynonyms #-}

module Phantom where

import Data.List

newtype Part (bool :: Bool) a = Part { unPart :: [a] }

MorrowM

module Main (main) where

import Codec.Picture
import Data.Bifunctor
import Data.Foldable
import Data.List
import Text.Printf

main :: IO ()
main = gif $ frameList (-20) 100