On Apr 18, 2016 4:18 PM, "David Feuer" <david.feuer@gmail.com> wrote:

If

f :: a -> IO a

for some a, and I want to use

mfix f

then f must not inspect its argument in any way, or the computation
will get stuck. In some cases, this seems a bit harsh. For example,

mfix (\x -> fmap (3 :) (x `seq` readLn))

looks perfectly reasonable. There is no need to inspect the return []
action to know that the final result of the computation will begin
with 3:. Is there a lazy IO mapping function somewhere that can work
such magic?