ticks

[BebeSparkelSparkel]

I just came across the unit ticks.

The value of this property represents the number of 100-nanosecond intervals that have elapsed since 12:00:00 midnight, January 1, 0001 in the Gregorian calendar

https://docs.microsoft.com/en-us/dotnet/api/system.datetime.ticks?view=netframework-4.8

[AshleyYakeley]

What kind of support for this did you have in mind?

[BebeSparkelSparkel]

Something like:

newtype Ticks = Ticks {_ticks :: Integer} deriving (Show, Eq, Ord, Num, Zero)
makeLenses ''Ticks
instance ToJSON Ticks where toJSON = toJSON . view ticks

divOf :: Integral a => a -> Iso' a a
divOf x = iso (`div` x) (* x)

multOf :: Integral a => a -> Iso' a a
multOf = from . divOf

posix :: Iso' Integer POSIXTime
posix =
  (iso MkFixed (\(MkFixed x) -> x) :: Iso' Integer Pico) .
  (iso secondsToNominalDiffTime nominalDiffTimeToSeconds :: Iso' Pico POSIXTime)

ticks2posix :: Iso' Ticks POSIXTime
ticks2posix =
  ticks .
  subtracting 621355968000000000 .
  multOf (10 ^ 5) .
  posix

[AshleyYakeley]

The time library has avoided the approach of having a type for each unit. Instead, it has a type for each concept, such as "absolute time" or "relative time" or, in this case, "POSIX time" due to the particular way POSIX ignores leap seconds. Ticks measure POSIX time, and the time library has the POSIXTime type for representing that.

The .NET DateTime.Ticks property has (.NET) type long, corresponding to Haskell Int64. Therefore we could have:

dotNetTicksToPosix :: Int64 -> POSIXTime
posixToDotNetTicks :: POSIXTime -> Int64

However, since "ticks" comes from .NET, it's not clear to me this belongs in the time library rather than some .NET-specific library.

[BebeSparkelSparkel]

Thanks