ghc-lens-datetime
Lenses for Data.Time.* types
The 'lens-datetime' library provides a unified lens based accessors to the various types in 'Data.Time.Clock', 'Data.Time.Calendar' and 'Data.Time.LocalTime'. This library only tries to make some of the common use-cases convenient, it doesn't aim for completeness. If you want completeness and/or efficiency try the 'thyme' package instead (<http://hackage.haskell.org/package/thyme>). Demonstration of basic uses.>import Control.Lens>import Data.Time>import Data.Time.Lens>>aDay :: Day>aDay = fromGregorian 2013 08 22>>aLocal :: LocalTime>aLocal = LocalTime aDay (TimeOfDay 13 45 28)>>aUTC :: UTCTime>aUTC = UTCTime aDay 7458.9 You can then do the following:>>aLocal ^. years>2013>>aUTC ^. months>8>>aLocal&time .~ midnight>2013-08-22 00:00:00>>aUTC&days .~ 1&months .~ 1>2013-01-01 02:04:18.9 UTC You can manipulate the date-time values with proper roll-over behavior via the 'FlexibleDateTime' mechanism:>>aLocal&flexDT.months +~ 12>2014-08-22 13:45:28>>aUTC&flexDT.days +~ 100>2013-11-30 02:04:18.9 UTC>>aLocal&flexDT.minutes +~ 120>2013-08-22 15:45:28>>aLocal&flexDT %~ ((days +~ 7) . (hours +~ 2))>2013-08-22 13:45:28.
BSD-3-Clause