[Haskell-beginners] get date

[Luca Ciciriello]

Ok this solve my problem.
I've just missed an IO before String in the type signature.

Thanks.

Luca.


On Jun 24, 2010, at 11:16 AM, Ozgur Akgun wrote:

> 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 <luca_ciciriello at hotmail.com> 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 <luca_ciciriello at hotmail.com> 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

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