# Pastebin HgYfkiew
{-# LANGUAGE TemplateHaskell #-}

import Control.Lens

newtype Foo a = Foo { _ayys :: [a] } deriving (Show)

newtype Bar = Bar { _bar :: Int } deriving Show

newtype Baz = Baz { _baz :: String } deriving Show

-- I normally use generic-lens these days but whatever.
$(makeLenses ''Foo)
$(makeLenses ''Bar)
$(makeLenses ''Baz)

foos :: [Foo Bar]
foos = [Foo [Bar 2, Bar 3], Foo [Bar 5], Foo [Bar 7, Bar 11, Bar 13]]

batch :: [Bar] -> IO [Baz]
batch = pure . map (Baz . show . _bar)

bars :: IO [Foo Baz]
bars = foos & unsafePartsOf (traverse . ayys . traverse) %%~ batch