lib/Hcompta/Data.hs

   1 {-# LANGUAGE ConstraintKinds #-}
   2 module Hcompta.Data where
   3
   4 import Data.Tuple (fst, snd)
   5
   6 -- * Class 'Has'
   7 type Has ty a = (Get ty a, Set ty a)
   8
   9 -- ** Class 'Get'
  10 class Get ty a where
  11         get :: a -> ty
  12 instance Get a (a, b) where get = fst
  13 instance Get b (a, b) where get = snd
  14
  15 -- ** Class 'Set'
  16 class Set ty a where
  17         set :: ty -> a -> a
  18 instance Set a (a, b) where set a (_, b) = (a, b)
  19 instance Set b (a, b) where set b (a, _) = (a, b)
  20
  21 -- * Class 'Iso'
  22 type Iso ty a = (To ty a, To a ty)
  23
  24 -- ** Class 'To'
  25 class To ty a where
  26         to :: a -> ty
  27 {-
  28 instance To a a where
  29         to = id
  30 -}