hmm otherwise the return False must be a return True, stupid bug:
-- don't re-fetch if I fetched in the last 2 hours
needToFetchAgain :: FilePath -> IO Bool
needToFetchAgain export_filename = do
exists <- doesFileExist export_filename
if (not exists)
then return True
else do
modif <- getModificationTime export_filename
curTime <- getClockTime
let diff = diffClockTimes curTime modif
return $ tdSec diff >= (3600*2) -- 2 hours
On Wed, Oct 31, 2012 at 11:25 AM, Emmanuel Touzery
Hello,
I am wondering if this code can be made a bit nicer?
I am checking if a file exists... and then if it exists I'm checking whether it's older than two hours from now. It is a bit annoying to have that second block in the else (i could make a second function but i think it all belongs in this function).
This structure makes me think about the Maybe monad, where it would automatically exit after it would find out that the file doesn't exists, instead of having a cascade of if statements inside one another.
But this function is already in the IO monad (maybe I'm thinking about this in the wrong way though).
Any idea for an improvement?
-- don't re-fetch if I fetched in the last 2 hours needToFetchAgain :: FilePath -> IO Bool needToFetchAgain export_filename = do exists <- doesFileExist export_filename if (not exists) then return False else do modif <- getModificationTime export_filename curTime <- getClockTime let diff = diffClockTimes curTime modif return $ tdSec diff >= (3600*2) -- 2 hours
Thank you!
Emmanuel