Re: [Haskell-cafe] Serializing UTCTimes
Bas van Dijk wrote: What's the recommended way for serializing (with the cereal package) an UTCTime? Serialize the Day part as an Integer using toModifiedJulianDay/ModifiedJulianDay, (Note that Day is not a constructor, it's just the name of the type.) Serialize the DiffTime as a Rational, as Ertugrul said. I'm now using the datetime package Why? It just obscures the time library. But I will have to look at the code of datetime to see if I'm not losing precision. You are losing precision. If you only care about time to the nearest second, you can truncate the Rational of the DiffTime (don't round, because this may be the last second of a day) and then use fromIntegral to deserialize. Regards, Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Serializing UTCTimes
Thanks Ertugrul and Yitzchak. I failed to notice the Real and Fractional instances for DiffTime. Thanks very much for pointing me to it. I dropped the dependency on datetime and implemented your suggestions. Bas On 21 January 2012 22:29, Yitzchak Gale g...@sefer.org wrote: Bas van Dijk wrote: What's the recommended way for serializing (with the cereal package) an UTCTime? Serialize the Day part as an Integer using toModifiedJulianDay/ModifiedJulianDay, (Note that Day is not a constructor, it's just the name of the type.) Serialize the DiffTime as a Rational, as Ertugrul said. I'm now using the datetime package Why? It just obscures the time library. But I will have to look at the code of datetime to see if I'm not losing precision. You are losing precision. If you only care about time to the nearest second, you can truncate the Rational of the DiffTime (don't round, because this may be the last second of a day) and then use fromIntegral to deserialize. Regards, Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Serializing UTCTimes
Hello, What's the recommended way for serializing (with the cereal package) an UTCTime? It's easy to give Serialize instances for UTCTime and Day: instance Serialize UTCTime where get = liftM2 UTCTime get get put (UTCTime day time) = put day put time instance Serialize Day where get = liftM Day get put = put . toModifiedJulianDay However I have no idea how to serialize the DiffTime stored in an UTCTime: instance Serialize DiffTime where get = ? put = ? Regards, Bas ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Serializing UTCTimes
On 20 January 2012 15:03, Bas van Dijk v.dijk@gmail.com wrote: What's the recommended way for serializing (with the cereal package) an UTCTime? I'm now using the datetime package so I can do: import Data.DateTime (fromSeconds, toSeconds) instance Serialize UTCTime where get = fromSeconds $ get put = put . toSeconds But I will have to look at the code of datetime to see if I'm not loosing precision. Bas ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Serializing UTCTimes
Bas van Dijk v.dijk@gmail.com wrote: However I have no idea how to serialize the DiffTime stored in an UTCTime: instance Serialize DiffTime where get = ? put = ? Note that DiffTime has this weird property that there is a Real instance, so you have a toRational function. ;) To go the other way you have a Fractional instance, so you also have 'fromRational'. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife = sex) http://ertes.de/ signature.asc Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
