Cofree animation

Lib.hs

module Lib where

import Control.Comonad.Cofree
import Control.Monad.Reader
import Control.Concurrent

drawBar :: Float -> IO ()
drawBar n = putStrLn (replicate (ceiling n) '#')

type Animation = Cofree (Reader Float) Float
animation :: Cofree (Reader Float) Float
animation = unfold go 0
  where
    go :: Float -> (Float, Reader Float Float)
    go n = ((1 + sin n) * 10, asks (+ n))

loop :: Animation -> IO ()
loop (a :< next) = do
    drawBar a
    threadDelay 10000
    loop (runReader next 0.1)