I read the discussion of Time Library organization, but did not feel like it arrived anywhere. The current design seems like it was expedient for its time, but does not feel particularly robust. It does not handle typical usecases well and provides little protection from user error. So I'm going to take a shot at a proposal: ---- The Y2K problem --------------- It would be nice if the library was explicit about whether year was 2 or 4 digits. Why not define year like this: newtype Year = Year Int -- don't export constructor mkYear century centyear = Year (100*century+centyear) mkBigYear millenium cent centyear = ... Allow Dates without Times ------------------- There are lots of contexts in which you want a date and not a time e.g. storing birthdates. Is there any reason the Time library shouldn't have a standard Date type e.g. data Date = {month::Month,day::Day,year::Year} Don't allow imposible weekdays ------------------------------ Weekday and yearday seem like they should be functions on this Date type and not part of the datastructure (you shouldn't be able to produce weekdays that don't match dates). weekDay::Date->WeekDay Don't allow impossible times ---------------------------- The type of hour minute and second should protect the user from 28 o'clock and making appointments for 31:101 PM So we probably want: data Hour = H0 | H1 | H2 ... H23 data Minute = M0 | M1 | M2 ... M59 data Second = S0 | S1 | S2 ... S59 data AMPM = AM | PM Times Types ----------- There are also lots of contexts where you want a time but not a date e.g. an alarm clock.... data Time = {hour::Hour ,minute::Minute ,second::Second ,millis::Int ,isDST::Bool, ,timeZone::TimeZone } If you have a leap second time that doesn't work in this model, round it! The 99.9999% case does not need to be sacrificed for the occasional physicist who need to know that the time is is 24:00:03. Re millis, yes it seems like it should be Rational, but this is human meaninful time. And humans don't care about millis. We can then produce a DateTime as data DateTime = DateTime {date::Date,time::Time} Epochal High Precision Time -------------------------- If you are doing physicist calculations, then use: data EpochTime a = EpochTime {seconds::Integer ,fraction::Ratio a ,precision::Integer } precision specifies the maximum size of the denominator of the fraction. epochTimeToDateTime::Epoch->DateTime The existing TimeDiff is totally bizarre. If tdSec == 3600 is that an error or is that the same as tdSec == 0 and tdHour == 1? How many months are a difference in months? It all seems too application specific to belong in a library. I don't have a particular good idea here. I think EpochTime does what you need in a library. The last major element we need is: getEpochTime::IO EpochTime Analogous to the old getClockTime but includes the resolution of the system clock. -Alex- ______________________________________________________________ S. Alexander Jacobson tel:917-770-6565 http://alexjacobson.com