[Haskell-cafe] Converting string to System.Time.ClockTime

[Antoine Latter]

On Thu, Dec 8, 2011 at 9:01 AM, dokondr <dokondr at gmail.com> wrote:
> Now, when I have managed to convert UTCTime to seconds (see code below) I
> got stuck trying to convert from UTCTime to CalendarTime, how to do this?
>
>

It might be easier to use 'diffUTCTime' and 'addUTCTime' instead of
converting to and from POSIX seconds.

What do you need the 'CalendarTime' for? I recommend not mixing the
'time' and 'old-time' packages if you can avoid it.

If you really need to for inter-operating with some other library, it
looks like you can use the 'datetime' package to convert from a
UTCTime to a ClockTime, and then you can use the 'old-time' package to
convert from a 'ClockTime' to a 'CalendarTime'.

Antoine

> import Data.Time.Format
> import Data.Time.Clock
> import Locale
> import Data.Maybe
> import Data.Time.Clock.POSIX
>
>
> s1 = "Wed, 07 Dec 2011 10:09:21 +0000"
> s2 = "Wed, 07 Dec 2011 10:11:00 +0000"
> t1 = fromJust $ tryParseTime s1
> t2 = fromJust $ tryParseTime s2
> pt1 = utcTimeToPOSIXSeconds t1  -- :: UTCTime -> POSIXTime
> pt2 = utcTimeToPOSIXSeconds t2
> pt3 = pt1 + (pt2 - pt1) / 2
> t3 = posixSecondsToUTCTime pt3
>
>
> t = compare t1 t2
>
> tryParseTime :: String -> Maybe UTCTime
> tryParseTime timeStr = tryFormat (parseTime defaultTimeLocale timeFormat1
> timeStr :: Maybe UTCTime)
>    where
>      tryFormat time
>         | time == Nothing = parseTime defaultTimeLocale timeFormat2 timeStr
> :: Maybe UTCTime
>         | otherwise = time
>
>      timeFormat1 = "%a, %d %b %Y %T %z"
>      timeFormat2 = "%m/%e/%Y %l:%M:%S %p"
> -- timeFormat1 = "%m/%d/%Y %l:%M:%S %p"
>
>
>
> On Thu, Dec 8, 2011 at 6:30 PM, dokondr <dokondr at gmail.com> wrote:
>>
>> I need to parse time strings like "Wed, 07 Dec 2011 10:09:21 +0000" to a
>> type that:
>> 1) implements Eq, Ord
>> 2) is numerical, so I could subtract one value from another to find the
>> difference or interval length
>>
>> To answer 1) requirement I wrote the following snippet. Yet I could not
>> subtract  UTCTime values. How can I convert them to milliseconds?
>>
>> import Data.Time.Format
>> import Data.Time.Clock
>> import Locale
>> import Data.Maybe
>>
>> s1 = "Wed, 07 Dec 2011 10:09:21 +0000"
>> s2 = "Wed, 07 Dec 2011 10:11:00 +0000"
>> t1 = fromJust $ tryParseTime s1
>> t2 = fromJust $ tryParseTime s2
>>
>> t = compare t1 t2
>>
>> tryParseTime :: String -> Maybe UTCTime
>> tryParseTime timeStr = tryFormat (parseTime defaultTimeLocale timeFormat1
>> timeStr :: Maybe UTCTime)
>>    where
>>      tryFormat time
>>         | time == Nothing = parseTime defaultTimeLocale timeFormat2
>> timeStr :: Maybe UTCTime
>>         | otherwise = time
>>
>>      timeFormat1 = "%a, %d %b %Y %T %z"
>>      timeFormat2 = "%m/%e/%Y %l:%M:%S %p"
>>
>>
>>
>>
>> On Thu, Dec 8, 2011 at 6:12 PM, Erik Hesselink <hesselink at gmail.com>
>> wrote:
>>>
>>> I'm not sure if you really need ClockTime (from old-time), but if you
>>> don't, the types from the 'time' package are all parseable with
>>> `parseTime` [1].
>>>
>>> Erik
>>>
>>> [1]
>>> http://hackage.haskell.org/packages/archive/time/latest/doc/html/Data-Time-Format.html#v:parseTime
>>>
>>> On Thu, Dec 8, 2011 at 14:16, dokondr <dokondr at gmail.com> wrote:
>>> > Hi,
>>> > What would be the simplest way to convert strings like "Wed, 07 Dec
>>> > 2011
>>> > 10:09:21 +0000" to System.Time.ClockTime ?
>>> >
>>> > Thanks!
>>> >
>>> >
>>> >
>>> > _______________________________________________
>>> > Haskell-Cafe mailing list
>>> > Haskell-Cafe at haskell.org
>>> > http://www.haskell.org/mailman/listinfo/haskell-cafe
>>> >
>>
>>
>>
>>
>>
>
>
>
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