avieth

{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE FunctionalDependencies #-}

avieth

{-# LANGUAGE GADTs #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE EmptyCase #-}

{-# OPTIONS_GHC "-fwarn-incomplete-patterns" #-}

avieth

{-# LANGUAGE GADTSyntax #-}

-- # Inter-node messages

-- | A single 'Message' type for all inter-node communication.
data Message where
  MessageControl  :: Control -> Message
  MessageDatum    :: Datum -> Message
  MessageAnnounce :: Announce -> Message
  MessageRequest  :: Request -> Message

avieth

{-# LANGUAGE GADTs #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeInType #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE RankNTypes #-}

import Data.Proxy

avieth

Interpreting Free Monads of Functor Sums
========================================

This text deals with a way to compose certain kinds of monads, thereby mixing
their capabilities. It is a literate Haskell file, so let's begin with a
bunch of noise.

> {-# LANGUAGE MultiParamTypeClasses #-}
> {-# LANGUAGE FlexibleInstances #-}
> {-# LANGUAGE FlexibleContexts #-}

avieth

-- This is in response to Robert Smallshire's talk titled
-- 'The Unreasonable Effectiveness of Dynamic Typing for Practical Programs'.
-- http://www.infoq.com/presentations/dynamic-static-typing/
-- Around the 30 minute mark he gives an example of what he calls a failure
-- of the F# type system, because it allows him to add energy to torque.
-- I demonstrate here that Haskell's type system is capable of ruling
-- out this nonsense. I have no experience with F#; maybe its type system
-- can do the same, if appropriately handled.

-- We'll need some multiparameter typeclasses.