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

-- Environment effects: ask and local.
--   ask reads the current environment value.
--   local f action runs action with the env transformed by f.
--
--   The CLI starts with an empty (Leaf) environment.  This demo uses
--   local to inject a real string so that ask returns something readable.

main = io <| 
  (bind 
  local (_ : "sandbox")
    (bind ask (env :
    bind (putStrLn (append "working in env: " env)) (_ :
    pure "inside-done"))))
  (outside :
    bind (putStrLn (append "local returned: " outside)) (_ :
    pure t))