puffnfresh

module GCounter

import Data.Vect

||| GCounter is a Conflict Free Replicated Datatype.
||| For a definition, see https://en.wikipedia.org/wiki/Conflict-free_replicated_data_type
||| It provides update, query and merge operations.
||| merge is commutative, associative and idempotent.
data GCounter : Nat -> Type where
  Nil : GCounter Z

puffnfresh

This is my short-ish tutorial on how to implement closures in
a simple functional language: Foo.

First, some boilerplate.

> {-# LANGUAGE DeriveFunctor, TypeFamilies #-}
> import Control.Applicative
> import Control.Monad.Gen
> import Control.Monad.Writer
> import Data.Functor.Foldable

puffnfresh

module Payments where

data Customer = Customer { name :: String, age :: Int } deriving (Eq, Ord, Show)

-- I know partial record fields is an anti-pattern, but who's counting?
data Payment
  = Cash { customer :: Customer, amount :: Double }
  | Credit { customer :: Customer, amount :: Double, cardNumber :: Int }
  | Check { customer :: Customer, amount :: Double, routingNumber :: Int, accountNumber :: Int }
  deriving (Eq, Ord, Show)