#!/bin/sh
#
# This is a shell archive.  To extract its contents,
# execute this file with /bin/sh to create the file(s):
#
# README		    busdays.ec
#
# This shell archive created: Fri Jul  3 10:58:15 CDT 1998
#
echo "Extracting file README"
sed -e 's/^X//' <<\SHAR_EOF > README
XSubject: Calculate working days using stored procedure
XFrom: Jonathan Leffler <jleffler@informix.com>
XDate: Mon, 29 Jun 1998 09:23:07 -0700 (PDT)
X
XOn Fri, 26 Jun 1998, Nils Myklebust wrote:
X> This is a slightly difficult problem with many solutions.  [...]
X
X> On Wed, 24 Jun 1998 22:36:22 GMT, sjsyau@my-dejanews.com wrote:
X> >Given:
X> >
X> >Today's date + Working Days
X> >Today's date - Working Days
X> >
X> >I need to find out the result in date format. The working days means to
X> >exclude weekends and holidays.
X
XOn 15th May 1998, under the subject 'Re: ESQLC and date/datetime routines',
XI posted some skeletal (and bug laden) ESQL/C code to add N business days
Xto a given date.  As far as I recall, I also posted a follow up on 18th May
Xwith a fully tested version of the code, but Dejanews denies any knowledge
Xof this.  I also thought I sent it to the IIUG, but that site seems to deny
Xit too.  I must be hallucinating.
X
XAnyway, here is a pair of ESQL/C routines which add N business days to a
Xgiven date, where N can be positive or negative.
X
X	typedef long Date;
X
X	/* Declaration should be in a header for use elsewhere! */
X	extern Date AddNBusinessDays(Date indate, int ndays);
X	extern Date AddNBusinessDaysHolidays(Date indate, int ndays);
X	extern int HolidaysBetween(Date d1, Date d2);
X
XAs distributed, the routines return the same answer.  There are hooks for
Xhandling holidays in AddNBusinessDaysHolidays() using the dummy function
XHolidaysBetween() which takes to dates and should return the number of
Xholidays (as opposed to weekend days) between the two specified dates (the
Xrange includes those dates).  The dummy version simply returns 0; if you
Xwant to record real holidays, rewrite the function to work the way you
Xthink it should.
X
XObviously, this isn't a direct answer to the question -- it is ESQL/C code
Xand not SPL code.  However, there is nothing in it that cannot be converted
Xinto SPL.  I'm not certain that it is the tightest possible algorithm;
Xthere may be other fancy tricks which compare start and end day-of-week
Xvalues and give you a better way of handling the weekends.  However, there
Xis test code which allows you to see that this produces what I regard as
Xthe correct answer.
X
XRemember that if your business works 6 days a week (like many retail
Xbusinesses), then the rules have to be changed.  Also, if your business
Xtakes Sunday and Monday off (again, this could be a shop), the rules change
Xagain.
X
XYours,
XJonathan Leffler (jleffler@informix.com) #include <witticism.h>
XGuardian of DBD::Informix -- see http://www.perl.com/CPAN
SHAR_EOF
if [ `wc -c < README` -ne     2568 ]
then
    echo "Lengths do not match -- Bad Copy of README"
fi
echo "Extracting file busdays.ec"
sed -e 's/^X//' <<\SHAR_EOF > busdays.ec
X/*
X@(#)File:            $RCSfile: busdays.ec,v $
X@(#)Version:         $Revision: 1.2 $
X@(#)Last changed:    $Date: 1998/05/18 17:32:22 $
X@(#)Purpose:         Calculate Business Days from Date
X@(#)Author:          J Leffler
X@(#)Copyright:       (C) JLSS 1998
X@(#)Product:         :PRODUCT:
X*/
X
X/*TABSTOP=4*/
X
X#include <sqlhdr.h>	/* rdayofweek() */
X
Xtypedef long Date;
X
X/* Declaration should be in a header for use elsewhere! */
Xextern Date AddNBusinessDays(Date indate, int ndays);
Xextern Date AddNBusinessDaysHolidays(Date indate, int ndays);
Xextern int HolidaysBetween(Date d1, Date d2);
X
X#ifndef lint
Xstatic const char rcs[] = "@(#)$Id: busdays.ec,v 1.2 1998/05/18 17:32:22 jleffler Exp $";
X#endif
X
XDate AddNBusinessDays(Date indate, int ndays)
X{
X	Date	outdate;
X	int	residue;
X	int	dw;
X
X	if (ndays == 0)
X		return indate;
X	dw = rdayofweek(indate);
X	if (ndays > 0)
X	{
X		outdate = indate + (ndays / 5) * 7;
X		residue = ndays % 5;
X		if (dw == 0)
X		{
X			outdate -= 2;
X			dw = 5;
X		}
X		else if (dw == 6)
X		{
X			outdate -= 1;
X			dw = 5;
X		}
X		outdate += residue;
X		if (dw + residue > 5)
X			outdate += 2;
X	}
X	else
X	{
X		ndays = -ndays;
X		outdate = indate - (ndays / 5) * 7;
X		residue = ndays % 5;
X		if (dw == 0)
X		{
X			outdate += 1;
X			dw = 1;
X		}
X		else if (dw == 6)
X		{
X			outdate += 2;
X			dw = 1;
X		}
X		outdate -= residue;
X		if (dw - residue < 1)
X			outdate -= 2;
X	}
X	return outdate;
X}
X
Xint HolidaysBetween(Date d1, Date d2)
X{
X	return 0;
X}
X
XDate AddNBusinessDaysHolidays(Date indate, int ndays)
X{
X	Date outdate = AddNBusinessDays(indate, ndays);
X	int nhols;
X
X	if (ndays > 0)
X	{
X		while ((nhols = HolidaysBetween(indate, outdate)) > 0)
X		{
X			indate = outdate;
X			outdate = AddNBusinessDays(indate, nhols);
X		}
X	}
X	else if (ndays < 0)
X	{
X		while ((nhols = HolidaysBetween(outdate, indate)) > 0)
X		{
X			indate = outdate;
X			outdate = AddNBusinessDays(indate, -nhols);
X		}
X	}
X	return outdate;
X}
X
X#ifdef TEST
X
X#include <stdio.h>
X
Xint main(void)
X{
X	Date refdate = 34567;	/* Mon 22 Aug 1994 */
X	Date curdate;
X	Date nxtdate;
X	int offset;
X	int daynum;
X	char buffer[60];
X	char *pad;
X
X	printf("Start Date     ");
X	for (offset = -8; offset < 9; offset++)
X		printf("  %-6d", offset);
X	putchar('\n');
X
X	for (daynum = 0; daynum < 7; daynum++)
X	{
X		curdate = refdate + daynum;
X		rfmtdate(curdate, "ddd dd mmm yyyy", buffer);
X		printf("%s", buffer);
X		pad = ": ";
X		for (offset = -8; offset < 9; offset++)
X		{
X			nxtdate = AddNBusinessDays(curdate, offset);
X			rfmtdate(nxtdate, "ddd dd", buffer);
X			printf("%s%s", pad, buffer);
X			pad = ", ";
X		}
X		putchar('\n');
X	}
X	return 0;
X}
X
X#endif /* TEST */
SHAR_EOF
if [ `wc -c < busdays.ec` -ne     2580 ]
then
    echo "Lengths do not match -- Bad Copy of busdays.ec"
fi
echo "Done."
exit 0