Hi David,

I believe the easiest way to do what you want is to use MonadReader class instead of explicit t (Reader [String] a):

push' :: MonadReader [String] m => String -> m a -> m a
push' s = local (s:)

Best,
Nick

2013/10/31 David Fox <dsf@seereason.com>

I can write a stack push function in the reader monad like so:

import Control.Monad.Reader

push :: String -> Reader [String] a -> Reader [String] a

push s action = local (s :) action

How can I write a push that works inside a monad transformer?

push' :: MonadTrans t => String -> t (Reader [String]) a -> t (Reader [String]) a

push' s action = ???

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