gistfile1.hs

{-# LANGUAGE TemplateHaskell, RankNTypes #-}
module Main where
import Control.Lens
import Control.Monad.State
import Data.List

sample :: [String]
sample =
  [ "hoge"
  , "piyo"
  , "fuga"
  , "hogehoge"
  , "piyopiyo"
  , "fugafuga"
  , "hogepiyo"
  , "piyofuga"
  , "fugahoge"
  , "hogepiyofuga"
  ]

inhoge :: Getter [String] [String]
inhoge = to (filter $ isInfixOf "hoge")

inpiyo :: Getter [String] [String]
inpiyo = to (filter $ isInfixOf "piyo")

infuga :: Getter [String] [String]
infuga = to (filter $ isInfixOf "fuga")

main :: IO ()
main = do
  print $ sample^.inhoge
  print $ sample^.inpiyo
  print $ sample^.infuga
  print $ sample^.inhoge.inpiyo
  print $ sample^.inpiyo.infuga
  print $ sample^.inhoge.inpiyo.infuga