snowleopard

{-# LANGUAGE GADTs, DataKinds, TypeOperators #-}
{-# OPTIONS_GHC -Wno-unticked-promoted-constructors #-}

-- This is an attempt to find a safer implementation for GHC constant folding algorithm
-- See https://ghc.haskell.org/trac/ghc/ticket/15569

-- Shapes of expression trees: L stands for a literal, V for a variable
data Shape = L | V | Shape :+: Shape | Shape :*: Shape

-- Arithmetic expressions with shape annotations

snowleopard

{-# LANGUAGE GADTs, ScopedTypeVariables, TypeOperators #-}
module CCC where

import Algebra.Graph.Undirected
import Prelude hiding ((.), id, repeat, round)
import Control.Category
import Control.Monad.Writer
import Data.List.Extra hiding (repeat)
import Data.Map.Strict (Map)
import Data.Void

snowleopard

(* See https://github.com/snowleopard/selective/blob/master/src/Control/Selective/Multi.hs *)

module Sigma (T : sig
  type 'a t
end) =
struct
  type t = Sigma : 'a T.t * 'a -> t
end

module type T = sig

snowleopard

-- See http://www.staff.city.ac.uk/~ross/papers/FingerTree.html
class Monoid m => Measured a m where
    measure :: a -> m

instance Measured a [a] where
    measure a = [a]

-- Generalised to any resulting monoid from `unfoldr :: (b -> Maybe (a, b)) -> b -> [a]`
unfoldr :: Measured a m => (b -> Maybe (a, b)) -> b -> m
unfoldr f b = case f b of