14 replies to this topic

[Glenn Meyers]

Suppose we have a bit of fun.

What is the fastest logic for calculating the number of days in that month for any given date that the logic is executed?

For example...the logic would return 28 if the routine was run any day in February. 30 for September. Etc.

Oh, and Merry Christmas you lot!

Glenn

[Mike Schoen]

convert yyyymm to string,
set dd to 31, cdate it to number
if > 0 done
try again fo 30,29,28

[Rick San Soucie]

Assumptions:

1) Using standard PRO-IV logic commands CDATE, PIC and CONV
2) Checking only within valid dates covered with CDATE
3) Date is entered into variable #D, stored in PRO-IV internal date format
4) Output is number of days, stored in string variable $DAYS
5) Looking for fewest logic statements


Logic:

$D = CDATE(#D,'YYYYMM')
IF $D(5,6) = '12' THEN $D = '31' EXIT;
#N = CDATE($D(1,4) + PIC(CONV($D(5,6)) + 1,'99') + '01','YYYYMMD
$DAYS = CDATE(#N - 1,'DD')

[Rick San Soucie]

I made a transfer error. The logic should have read:

$D = CDATE(#D,'YYYYMM')
IF $D(5,6) = '12' THEN $DAYS = '31' EXIT;
#N = CDATE($D(1,4) + PIC(CONV($D(5,6)) + 1,'99') + '01','YYYYMMD
$DAYS = CDATE(#N - 1,'DD')

[Rob Donovan]

Rick,

It could be a problem with the forum not liking all those quotes and brackets. You could try with double quotes instead.. I'll take a look at it later.

Rob D.

[Cleve Haynes]

How about this global logic:

N PARMS(#D)

$M = CDATE(#D, 'MM')

WHILE CDATE(#D, 'MM') = $M
#D += 1
ENDWHILE

RETURN(CONV(CDATE(#D - 1, 'DD')))

[Jonathan Weeks]

#N = CONV(CDATE(CDATE(CDATE(@DATE,'YYYY')
+ PIC(REM(CONV(CDATE(@DATE,'MM')) + 1,12),'99')
+ '01','YYYYMMDD') - 1,'DD'))

[Richard Bassett]

Very cute (although I think you may have omitted to increment the REM-expression to get a valid month).

[Richard Bassett]

If the operation is going to be done several times in a function, the fastest way is very probably the not-much-fun way eg:

Initialize an array with the number of days in each month..

DEFINE #MonthLength(12, 2.0)

#MonthLength(1) = 31

#MonthLength(2) = -99   [won't be using this one]

#MonthLength(3) = 31

etc..

Then when you need a day count use something classical like..
(I know, I know, leap centuries..
but there aren't any more within the range of ProIV)

$month = CDATE(#theDate, 'MM')

IF $month <> '02' THEN

  #dayCount = #MonthLength(CONV($month))

ELSE

  IF REM(CONV(CDATE(#theDate,'YYYY')), 4) = 0 THEN

    #dayCount = 29

  ELSE

    #dayCount = 28

  ENDIF

ENDIF

Or (under the influence of Jonathan) something like..

$date = CDATE(#theDate, 'YYYYMMDD')

IF $date(5,6) <> '02'

  #dayCount = #MonthLength(CONV($date(5,6)))

ELSE

  #dayCount = CONV( CDATE( CDATE($date(1,4) + '0301', 'YYYYMMDD') - 1, 'DD') )

ENDIF

A Merry Christmas to those who celebrate it
and Happy Holidays to those who don't

[Richard Bassett]

Oops - what I should have said was that it seems the increment should be outside the REM-expression

[Richard Bassett]

Funny.
That's what my girlfriend said.

Is this better?

    STEP CONV(CDATE(@DATE, 'MM'))

1   #days = 31

2   #days = CDATE(CDATE(@DATE,'YYYY') + '03' + CDATE(@DATE, 'DD'), 'YYYYMMDD) - @DATE

3   #days = 31

4   #days = 30

5   #days = 31

6   #days = 30

7   #days = 31

8   #days = 31

9   #days = 30

10  #days = 31

11  #days = 30

12  #days = 31

[Ralph Gadsby]

Mike Schoen was pipped at the post by Richard Bassett's last entry (which I modified to use CALL instead of STEP, to make the code reuseable in a loop).

The wooden spoon goes to Cleve Haynes, whose routine took almost 20 times as long as the winning entry and had to be changed to make it safe (call by reference).

Full results (in seconds) for 222308 iterations using a range of dates between 1/1/1800 and the current date are as follows:

R Bassett 2
M Schoen 4
R Bassett 6
R San Soucie 7
J Weeks 12
C Haynes 37

Ralph

[Jonathan Weeks]

String CASEs are faster than numerics:

CASE CDATE(#D,'MM')

  WHEN '02':

    #E = 28

    #Y = CONV(CDATE(#D,'YYYY'))

    IF REM(#Y,4) ELSE    

       #E += 1

       IF REM(#Y,100) ELSE            

          #E -= 1                              

          IF REM(#Y,400) ELSE #E += 1;

       ENDIF

    ENDIF       

  WHEN '04','06','09','11': #E = 30

  OTHERWISE: #E = 31

ENDCASE

[Glenn Meyers]

This is almost the solution I used.
I did the month conversion to a number for a bit faster comparisions:
#M = CONV(CDATE (#D,'MM'))
CASE #M .....etc.
I also inverted the order of case checking to check for the most likely scenario (months with 31 days) first.