[Haskell-cafe] TimeDiff to Int?

Lyle Kopnicky lists at qseep.net
Wed Nov 12 11:10:57 EST 2008

Hi folks,

I had some code using the oldtime package, and want to convert it to use the
time package.

One of the things I need to do is calculate the number of seconds since
midnight. The easy part is getting a TimeDiff result:

utc <- getCurrentTime
tz <- getCurrentTimeZone
let td = timeOfDayToTime $ localTimeOfDay $ utcToLocalTime tz utc

Now td is a TimeDiff representation of the number of seconds since midnight.
It prints nicely, but I'm having a heck of a time figuring out how to
truncate it to an Int.

The floor function is only supported by the RealFrac class. Although
TimeDiff has an instance of RealFrac and Fractional, it doesn't have an
instance of RealFrac. I looked up the various to* and from* functions and
have come up short. fromEnum yields an Int but it's the wrong value. I know
I could use show and then use readS to get an Integer, or use formatTime
(and reparse that), but that's a hack.

I can convert it to a TimeOfDay which gives me hours, minutes, and seconds,
but then I have to do arithmetic on it, and the seconds are of type Pico,
which I can't call floor on either. I can convert it to a Rational via
timeOfDayToDayFraction, but a TimeDiff is already a Rational those don't
have floor.

What am I missing? There has got to be an easy way to count seconds!

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