Take a look at the monad-loops package.
Cheers,
Greg
On 12/13/2010 06:15 AM, Jacek Generowicz wrote:
-- Is it possible to rewrite code written in this style
untilQuit = do
text <- getLine
report text
if text == "quit"
then return ()
else untilQuit
-- in a style using higher order functions for abstract iteration? For
-- example, something along these lines:
untilQuit' = (fmap (takeWhile (/= "quit"))) (sequence $ map (>>=
report) (repeat getLine))
-- The latter version shows the report, but it doesn't stop at the
-- appropriate place, so I'm guessing that I'm being bitten by my
-- ignorance about the interaction of actions and lazyness.
-- For completeness, here's a definition of report
report text = do
putStrLn $ "You wrote " ++ text
return text
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