Config.hs

module Config (Config, config, dir, enqueue) where

import Data.Sequence (Seq, empty, (|>))
import qualified Data.Foldable as F

data Config = Config {
    dir :: String
  , seq :: Seq String
} deriving (Show)

config dir = 
  Config dir empty

enqueue :: Config -> [String] -> Config
c `enqueue` urls = 
    Config (dir c) q'
  where
    q' = foldl (|>) (Config.seq c) urls

-- TODO: make an instance of Foldable?
instance F.Foldable Config where
  foldr f z c =
      Config (dir c) q'
    where
      q' = F.foldr f z (Config.seq c)

  foldMap f c = 
      Config (dir c) q'
    where
      q' = F.foldMap f (Config.seq c)
  

Error:

[1 of 1] Compiling Config           ( src/Config.hs, interpreted )

src/Config.hs:21:21:
    Kind mis-match
    The first argument of `F.Foldable' should have kind `* -> *',
    but `Config' has kind `*'
    In the instance declaration for `F.Foldable Config'
Failed, modules loaded: none.