Enumerating Haskell data constructors

Extras.hs

module Extras where

-- | Create a list of all of the data constructors for a given type.
enumAll :: (Bounded a, Enum a) => [a]
enumAll = [minBound .. ]

Scratch.hs

module Scratch where

import Extras (enumAll)

data OS
  = GnuPlusLinux
  | OpenBSD
  | Mac
  | Windows
  deriving (Eq, Show, Bounded, Enum)

data ProgLang
  = Haskell
  | Agda
  | Idris
  | PureScript
  deriving (Eq, Show, Bounded, Enum)

data Programmer
  = Programmer
  { os :: OS
  , pl :: ProgLang
  } deriving (Eq, Show)

-- | Create a list of all possible programmers.
programmers :: [Programmer]
programmers =
  [Programmer os pl | os <- enumAll, pl <- enumAll]