!import "base" !Local
!import "list" !Local
!import "io"   !Local

-- Mutable state via get and put.
--   get reads the current state.
--   put replaces the state.
--
--   The CLI starts with an empty (Leaf) state.  This demo puts
--   readable strings and prints them back out.

main = io <|
  bind (put "idle") (_ :
  bind get (s1 :
  bind (putStrLn (append "state: " s1)) (_ :
  bind (put "running") (_ :
  bind get (s2 :
  bind (putStrLn (append "state: " s2)) (_ :
  bind (put "done") (_ :
  bind get (s3 :
  bind (putStrLn (append "state: " s3)) (_ :
  pure t)))))))))