Date math again...

[Bob Stockler]

John Esak wrote (on Wed, Jan 04, 2006 at 06:23:35PM -0500):

| Joe's off-the-top was pretty good. I thought about it for a moment and said
| to myself that would be too hard to work out let alone explain it. :-)  Very
| good.
| 
| Ken's... I put in my "keep" folder and will be thinking about it still when
| ever I go back to find it again. :-)  I hear 7x + y and think, uh-oh,
| quadratic equations again! :-)  No, seriously, another great idea.
| 
| Unfortunately, everyone is right about the holidays. Just put them in t
| lookup file and check if any of the lookup file "dates" fall between or
| equal to the start date and end date. Checking a hard coded array or
| variable list would be clumsy and slower I think then one quick lookup...

I've been playing with it a bit myself, and think that a lookup
to a holidays file would be more expensive that a gosub to a
subroutine (every date checked that is not a Sat or Sun would
require a lookup, and require maintaining two different files).

I visualize the whole thing as being a CALLed table that has only
to be edited once a year (sometime after the following year's
calendar is available - cron could bug the programmer as to when).

The called table checks the DOW() if the day-of-the-week is Sat
or Sun, and then, if not, a gosub in it checks in a subroutine in
it to see if the date being checked is a non-work day.

      If: Day eq "02/20/2006"   ' Presidents' Day (moveable)
    Then: YesNo = "1" ; return
      If: Day eq "05/30/2006"   ' Memorial Day (fixed)
    Then: YesNo = "1" ; return
      If: Day eq "07/04/2006"   ' Indepenence Day (fixed)
    Then: YesNo = "1" ; return
     ...
    Then: YesNo = "" ; return

I think that would be a lot less expensive of programmer (and CPU)
time, involving programmer time but once a year and much less CPU
and HD time doing lookups.

Bob

PS - I wrote a program (datecalc) using AWK that calculates the
     days between any two dates between 01/01/0001 to 12/31/9999.
     It also can tell the day-of-week of any day in that period.

PSS - I also wrote another AWK program (hcal) that prints the
      highlighted date in the centered calendar of a 3-month
      calendar for the entered date in the same range as above.
      If you don't believe it, get it and enter: "hcal 9/1/1752".
      It also prints a 12-month calendar for any year in that
      period. 

PSPS - I'll email these to anyone who requests them OFF LIST
       (if you're not on an OS that has an AWK, don't ask).

-- 
Bob Stockler  +-+  bob at trebor.iglou.com  +-+  http://members.iglou.com/trebor
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