Re: last day of month (was MIDRANGE-L Digest V2 #1546)

["Nelson C. Smith" <ncsmith@xxxxxxxx>]

Wouldn't all this be so much simpler if we just had the inverse of the
EXTRCT opcode?  Why wasn't it built at the same time as EXTRCT?

-----Original Message-----
From: bmorris@ca.ibm.com <bmorris@ca.ibm.com>
To: MIDRANGE-L@midrange.com <MIDRANGE-L@midrange.com>
Date: Friday, October 15, 1999 2:24 PM
Subject: RE: last day of month (was MIDRANGE-L Digest V2 #1546)


>
>
>
>>Date: Thu, 14 Oct 1999 09:16:48 -0700
>>From: Jon Erickson <jerickson@800.com>
>>
>>Correct me if I'm wrong,
>> ...
>>
>>d                 DS
>>d Isodate                         d   Inz
>>d  Isoyyyy                       4  0 Overlay(Isodate)
>>d  Isomm                         2  0 Overlay(Isodate:6)
>>
>>c                   Eval      Isoyyyy = Pyear
>>c                   Eval      Isomm = Pmonth
>>Add 1 month via ADDDUR
>>c                   AddDur    1:*Months     Isodate
>>
>>Subtract 1 day via SUBDUR
>>c                   SubDur    1:*Days       Isodate
>
>Sure, that will work.  I was discussing Jon's code to solve the general
case of
>getting the last day of the month containing a given date.
>
>Jon's code can be made to run a bit more quickly using overlays (you can
get rid
>of the extract by just setting the days part to "01").  Maybe that's a good
>idea,
>maybe not - it seems to me that using overlays makes the code a bit more
>complex.
>
>If you start with numeric year and month as in your example, your way is as
good
>as any.
>
>Hmm, I just thought of a way to use numeric year and month input avoiding
>overlays, with a single adddur:
>
>D date            s               d       datfmt(*iso) inz(D'0001-01-31')
> * Find the number of months after 0001-01 for the given year and month
> * E.g. for 0002-03, there are 12 + 1 months
>C                   eval      Pmonth = ((Pyear - 1) * 12) + (Pmonth - 1)
> * Add them to Jan 31, 0001.  Month-end adjustment will fix up any results
> * where the number of days in the month is less than 31.
>C                   adddur    Pmonth:*m     date
>
>With date operations, the contest should be regarding the number of date
>opcodes,
>not the number of statements.  (Date opcodes are very expensive.)
>
>Barbara Morris
>
>
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