Allan Lukwago epicallan

Some thoughts on building software

Lately I have been busy reading some new books on Domain Driven Design (DDD) and software architecture -- including a short yet eye-opening one in Python and a great one in F#. At the same time, it seems that more people in the Functional Programming world are looking at more formal approaches to modelling -- some examples here. This has brought some thought from the background of my brain about how we should model, organize, and architect software using the lessons we've learnt from functional programming.

Before moving on, let me be clear about this being just a dump of some thoughts, not always well-defined, definite

Optics By Example Cheat Sheets

The following are appendices from Optics By Example, a comprehensive guide to optics from beginner to advanced! If you like the content below, there's plenty more where that came from; pick up the book!

Operators
Composition Guide
Substitution Guide
Optical Constarints and Types

Operator Cheat Sheet

I started writing this polemic to answer your question, but I ended up touching on most of my gripes with Haskell in general, not just in a corporate context.

GHC

GHC is a modern compiler with an amazing RTS and tons of features, but I have some issues with it.

Monolithic and Hard to Contribute To

Reddit discussion.

Disclaimer 1: Type classes are great but they are not the right tool for every job. Enjoy some balance and balance to your balance.

Disclaimer 2: I should tidy this up but probably won’t.

Disclaimer 3: Yeah called it, better to be realistic.

Type classes are a language of their own, this is an attempt to document features and give a name to them.

	timestamp :: String -> Q a -> Q a
	timestamp name action = do
	start <- runIO getCurrentTime
	runIO $ putStrLn $ "Starting " <> name <> ": " <> show start
	a <- action
	end <- runIO getCurrentTime
	runIO $ do
	putStrLn $ "Ending " <> name <> ": " <> show end
	putStrLn $ "Elapased " <> name <> ": " <> show (diffUTCTime end start)
	pure a

	{-# LANGUAGE DataKinds #-}
	{-# LANGUAGE DeriveAnyClass #-}
	{-# LANGUAGE DeriveGeneric #-}
	{-# LANGUAGE DerivingStrategies #-}
	{-# LANGUAGE FlexibleContexts #-}
	{-# LANGUAGE FlexibleInstances #-}
	{-# LANGUAGE MultiParamTypeClasses #-}
	{-# LANGUAGE RankNTypes #-}
	{-# LANGUAGE RecordWildCards #-}
	{-# LANGUAGE TemplateHaskell #-}

	{-# LANGUAGE ConstraintKinds, DataKinds, DeriveGeneric, DerivingVia #-}
	{-# LANGUAGE ExplicitNamespaces, FlexibleContexts, FlexibleInstances #-}
	{-# LANGUAGE GADTs, GeneralizedNewtypeDeriving, MultiParamTypeClasses #-}
	{-# LANGUAGE PolyKinds, ScopedTypeVariables, StandaloneDeriving #-}
	{-# LANGUAGE TypeApplications, TypeFamilies, TypeInType, TypeOperators #-}
	{-# LANGUAGE UndecidableInstances #-}
	{-# OPTIONS_GHC -Wall #-}
	module Data.Aeson.Generic.DerivingVia
	( StrFun(..), Setting(..), SumEncoding'(..), DefaultOptions, WithOptions(..)
	, -- Utility type synonyms to save ticks (') before promoted data constructors

	{-# LANGUAGE DeriveGeneric #-}
	{-# LANGUAGE DerivingStrategies #-}
	{-# LANGUAGE FlexibleContexts #-}
	{-# LANGUAGE GeneralizedNewtypeDeriving #-}
	{-# LANGUAGE TemplateHaskell #-}
	{-# LANGUAGE TypeApplications #-}
	{-# LANGUAGE TypeOperators #-}
	{-# LANGUAGE UndecidableInstances #-}

	module Via where

	{-# LANGUAGE GADTs #-}
	{-# LANGUAGE PolyKinds #-}
	{-# LANGUAGE FunctionalDependencies #-}
	{-# LANGUAGE MultiParamTypeClasses #-}
	{-# LANGUAGE TypeOperators #-}
	{-# LANGUAGE DataKinds #-}
	{-# LANGUAGE KindSignatures #-}
	{-# LANGUAGE TemplateHaskell #-}
	{-# LANGUAGE FlexibleInstances #-}
	{-# LANGUAGE OverloadedLabels #-}