| Safe Haskell | Safe-Infered |
|---|
Data.Time.Lens
- class HasTime a where
- hours :: HasTime a => Lens a Int
- minutes :: HasTime a => Lens a Int
- seconds :: HasTime a => Lens a Pico
- class HasDate a where
- year :: HasDate a => Lens a Integer
- month :: HasDate a => Lens a Int
- day :: HasDate a => Lens a Int
- gregorian :: HasDate a => Lens a (Integer, Int, Int)
- class HasTime a => HasTimeZone a where
- data Day
- data TimeOfDay
- data LocalTime
- data ZonedTime
- getZonedTime :: IO ZonedTime
- data Lens a b
- getL :: Lens a b -> a -> b
- modL :: Lens a b -> (b -> b) -> a -> a
- setL :: Lens a b -> b -> a -> a
Time
The semantics of getL for time lenses (time,hours,minutes,seconds)
is straightforward.
The semantics of setL is to «normalize» the time before setting. Hence
modL minutes (+5)
>>>modL minutes (+5) (TimeOfDay 16 57 13)17:02:13
If this means crossing a day boundary, the semantics varies for different
structures. For structures that have a date component (i.e. for instances of
HasDate) the date is adjusted appropriately.
>>>modL hours (+10) (LocalTime (fromGregorian 2012 05 23) (TimeOfDay 16 57 13))2012-05-24 02:57:13>>>modL seconds (subtract 1) (LocalTime (fromGregorian 2012 05 23) (TimeOfDay 0 0 0))2012-05-22 23:59:59
If there's no date, the time is simply wrapped around.
>>>modL seconds (subtract 1) (TimeOfDay 0 0 0)23:59:59
Date
In contrast to time, the date lens is a simple accessor (it doesn't make
sense to «normalize» a Day).
Instead, setters for year, month and day have special semantics
described below.
Getters are always straightforward.
year :: HasDate a => Lens a IntegerSource
modL year (+n)n years, matching month and day, with Feb 29th
rolled over to Mar 1st if necessary (like addGregorianYearsRollOver)
month :: HasDate a => Lens a IntSource
modL month (+n)n months, with days past the last day of the
month rolling over to the next month (like addGregorianMonthsRollOver)
gregorian :: HasDate a => Lens a (Integer, Int, Int)Source
The semantics of gregorian corresponds to that of toGregorian and
fromGregorian
Time zone
class HasTime a => HasTimeZone a whereSource
Instances
Re-exports from Data.Time
data Day
The Modified Julian Day is a standard count of days, with zero being the day 1858-11-17.
data TimeOfDay
Time of day as represented in hour, minute and second (with picoseconds), typically used to express local time of day.
data LocalTime
A simple day and time aggregate, where the day is of the specified parameter, and the time is a TimeOfDay. Conversion of this (as local civil time) to UTC depends on the time zone. Conversion of this (as local mean time) to UT1 depends on the longitude.
data ZonedTime
A local time together with a TimeZone.