extensible is a library for extensible data types. It provides extensible product and sum types parameterized by type-level lists.
This tutorial introduces extensible records, an application of the extensible products.
First, we pass a space-separated list of field names to mkField:
{-# LANGUAGE TemplateHaskell, DataKinds, TypeOperators, FlexibleContexts #-}
{-# OPTIONS_GHC -fno-warn-unticked-promoted-constructors #-}