Hi Dananji!
First of all, for more explicit failure-handling I suggest using "readMay"
from package "safe" [0] instead of "read" whenever possible.
Alternative to using "read", if you know date format of input-data, you can
take a look at "UNIX-style parsing" section at Data.Time.Format module [1].
If you have older "time" package, you'd probably use parseTime, for newer
versions it is recommended to use parseTimeM.
Here's an example:
```
➜ ~ ghci
GHCi, version 7.8.4: http://www.haskell.org/ghc/ :? for help
Prelude> import Data.Time.Format
Prelude Data.Time.Format> import System.Locale
Prelude Data.Time.Format System.Locale> import Data.Time.Clock
Prelude Data.Time.Format System.Locale Data.Time.Clock> parseTime
defaultTimeLocale "%F %X" "2014-01-02 11:12:30" :: Maybe UTCTime
Just 2014-01-02 11:12:30 UTC
```
If you have a value of type "IO <something>", you can "extract" it when
being in IO monad like this:
main = do
currentTime <- getCurrentTime
-- in all remaining code, currentTime has type "UTCTime"
...
getDifference currentTime userTime
In terms of "sugar-less" way to use a value from "IO <something>", you can
also use it like this:
getCurrentTime >>= \currentTime -> doSomething currentTime
Hope this helps.
[0]: https://hackage.haskell.org/package/safe
[1]:
http://hackage.haskell.org/package/time-1.5.0.1/docs/Data-Time-Format.html
On Thu, May 14, 2015 at 10:20 AM, Dananji Liyanage
Hi All,
I'm trying out the date time conversions in Haskell.
How do I convert a keyboard input (IO String) to UTCTime?
This is how I'm doing (probably there's a better way), convDay x = read (x ++ " 00:00:00") :: UTCTime
Another thing, how do I convert getCurrentTime (IO UTCTime) to UTCTime in order to get the time difference between the keyboard input date and today?
-- Regards, Dananji Liyanage
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