Thanks Felipe. Yes I use getCurrentTime. But I found I a stupid error in my code. Now all works fine. Thanks anyway for your answer. Luca. On Jun 23, 2010, at 8:13 PM, Felipe Lessa wrote:

On Wed, Jun 23, 2010 at 08:03:16PM +0200, Luca Ciciriello wrote:

...

How can I get the current system date-time in Haskell?

I've used the library Time, but on MacOS X 10.6.4 the year is always 0.

Luca.

Do you mean, you used getCurrentTime from the time package[1]? What does the following line do?

(toGregorian . utctDay) `fmap` getCurrentTime

On my system,

GHCi, version 6.10.4: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Prelude> :m Data.Time Prelude Data.Time> (toGregorian . utctDay) `fmap` getCurrentTime Loading package old-locale-1.0.0.1 ... linking ... done. Loading package time-1.1.4 ... linking ... done. (2010,6,23)

http://hackage.haskell.org/packages/archive/time/1.2.0.3/doc/html/Data-Time-...

HTH,

-- Felipe.

On 24 June 2010 10:52, Luca Ciciriello wrote:

Just a question. How can I obtain a String from

currentTime :: IO Day currentTime = utctDay `fmap` getCurrentTime

Here currentTime returns to me 2010-06-24, but I want "2010-06-24". In another worlds I need a function

I bet Day has a Show instance (that's why you get 2010-06-24 in ghci I suppose) Just use that.

currentTimeStr :: IO Day -> String

Getting out of IO? I would think again. Following might be what you really want: currentTimeStr :: IO Day -> IO String

Any Idea?

Luca.

Best, Ozgur

Then you might want to use something like: currentTimeStr :: IO String currentTimeStr = do ct <- currentTime return ("File creation date: " ++ show ct ++ " by MyCompany") Or more concisely, currentTimeStr :: IO String currentTimeStr = liftM (\ ct -> "File creation date: " ++ show ct ++ " by MyCompany" ) currentTime My point is, the type of currentTimeStr is IO String, not just String. Because you are working on an IO value. Best, PS: If you are not confident with the piece of code I've suggested, please have a look at the io/monads/do-notation sections of the Real World Haskell. On 24 June 2010 11:17, Luca Ciciriello wrote:

Starting from the beginning, my original problem is to create the string:

"File creation date: " ++ currentSystemDate ++ " by MyCompany"

to obtain the string

"File creation date: 2010-06-24 by MyCompany"

Probably this is really trivial, but I'm a real beginner in Haskell and this seems to me a big problem.

Luca.

On Jun 24, 2010, at 9:59 AM, Ozgur Akgun wrote:

On 24 June 2010 10:52, Luca Ciciriello wrote:

...

Just a question. How can I obtain a String from

currentTime :: IO Day currentTime = utctDay `fmap` getCurrentTime

Here currentTime returns to me 2010-06-24, but I want "2010-06-24". In another worlds I need a function

I bet Day has a Show instance (that's why you get 2010-06-24 in ghci I suppose) Just use that.

...

currentTimeStr :: IO Day -> String

Getting out of IO? I would think again. Following might be what you really want:

currentTimeStr :: IO Day -> IO String

...

Any Idea?

Luca.

Best, Ozgur

-- Ozgur Akgun

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 6/24/10 03:52 , Luca Ciciriello wrote:

Just a question. How can I obtain a String from

currentTime :: IO Day currentTime = utctDay `fmap` getCurrentTime

Here currentTime returns to me 2010-06-24, but I want "2010-06-24". In another worlds I need a function

currentTimeStr :: IO Day -> String

You can't escape from IO, but you can lift a formatter into IO. Formatters are in Data.Time.Format; look at the documentation for your system's strftime() function to see how it works. - -- brandon s. allbery [linux,solaris,freebsd,perl] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkwjZuIACgkQIn7hlCsL25UwpgCfRuhCW5sB9G8Ud9Ci3JUZbVTt vAIAn3CFOoX9Q4etASv3ggC8KFxm94W6 =ZUFJ -----END PGP SIGNATURE-----