Comments on: Haskell and Time

By: Magnus

Magnus — Thu, 15 Jan 2009 22:52:35 +0000

@Mechanic, I think you've got it the wrong way around. One would use fromInteger to convert an integer to POSIXTime.

In both your examples you are trying pass a POSIXTime to fromInteger, as expected you get type errors when you do that.

Mechanic — Thu, 15 Jan 2009 18:27:44 +0000

I don't understand how to do this conversion, please, explain:

fromInteger 43 :: POSIXTime 43s

but

getPOSIXTime >>= (return . fromInteger)

:1:28: Couldn't match expected type time-1.1.2.2:Data.Time.Clock.UTC.NominalDiffTime' against inferred typeInteger'

or another example

Prelude Data.Time.Clock.POSIX> a <- getPOSIXTime Prelude Data.Time.Clock.POSIX> :type a a :: POSIXTime Prelude Data.Time.Clock.POSIX> fromInteger a

:1:12: Couldn't match expected type Integer' against inferred typePOSIXTime'

Magnus — Wed, 17 Sep 2008 07:48:01 +0000

@Micha & Andy: thanks for pointing that out.

Andy — Tue, 16 Sep 2008 23:57:01 +0000

fromIntegral 1221603766 :: POSIXTime seems to work too, though it isn't much shorter.

Micha? Bartoszkiewicz — Tue, 16 Sep 2008 23:52:37 +0000

You can use fromInteger from the Num class:

> fromInteger 42 :: POSIXTime
42s