On 19-Oct-1999, George Russell <[EMAIL PROTECTED]> wrote:
> The problem is that both behaviours are desirable. Sometimes you want
> to say "1 month from now"; sometimes "30 days from now". I think there
> is an obvious logical solution to this. Make the two kinds of time difference
> have different types. Thus
> class TimeDiff a where
> addToClockTime :: a -> ClockTime -> ClockTime
> diffClockTimes :: ClockTime -> ClockTime -> a
> Have types all instances of TimeDiff
> TimeDiff = TimeDiff Integer -- time in picoseconds
> TimeDiffDays = TimeDiffDays Int -- time in days
> TimeDiffMonths = TimeDiffMonths Int -- time in months
> (We don't actually need any more, since a second is always 10^12 picoseconds,
> a year is always -- in the Gregorian Calendar -- 12 months, and so on. But
> we could easily add them.)
A minute is always 60 seconds... except when there is a leap second.
So I think you need TimeDiffMinutes too. You might as well include
all of them.
--
Fergus Henderson <[EMAIL PROTECTED]> | "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh> | of excellence is a lethal habit"
PGP: finger [EMAIL PROTECTED] | -- the last words of T. S. Garp.
