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From: mose@ns.ccsn.edu (Russell Mosemann)
Subject: Re: Friday 13th, try it yourself (was Language Wars..)
Date: 1996/09/21
Message-ID: <R.521pfp$kec@ns.ccsn.edu>#1/1
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distribution: inet
references: <51bv60$8d@pheidippides.axion.bt.co.uk>
 		<32406D89.233E@watson.ibm.com> <uf3f0fmmrh.fsf@zen.microlise.co.uk>
 <3242D1EB.3F54@ford.com>
organization: Concordia College, Seward, NE
newsgroups: 
 comp.lang.ada,comp.lang.apl,comp.lang.basic,comp.lang.c,comp.lang.fortran,comp.lang.perl.misc,comp.lang.pl1,comp.lang.rexx,comp.lang.pascal.misc,comp.lang.smalltalk
Date: 1996-09-21T00:00:00+00:00
List-Id: <comp.lang.ada>


Reposting article removed by rogue canceller.

Clinton Pierce <cpierce1@ford.com> writes:

>See for yourself if the "Friday the 13th" thing is just a UL.  If you trust
>UNIX's 'cal' program, and that it does the Right Thing with Leap Years, the
>Gregorian/Julian switch etc..etc... This Perl script will show you the Truth:

   I decided to write a script of my own for Solaris 2.4 and perl
5.003 which calls cal for 1066 to 1996 and rips out the Fridays.  The
following is the number of times a particular day of the month falls
on a Friday.  The results are pretty evenly distributed, i.e. it is an
Urban Legend.

Day of month: 1 Freq: 1600
Day of month: 2 Freq: 1594
Day of month: 3 Freq: 1596
Day of month: 4 Freq: 1594
Day of month: 5 Freq: 1593
Day of month: 6 Freq: 1601
Day of month: 7 Freq: 1593
Day of month: 8 Freq: 1600
Day of month: 9 Freq: 1594
Day of month: 10 Freq: 1596
Day of month: 11 Freq: 1594
Day of month: 12 Freq: 1593
Day of month: 13 Freq: 1601
Day of month: 14 Freq: 1593
Day of month: 15 Freq: 1601
Day of month: 16 Freq: 1594
Day of month: 17 Freq: 1596
Day of month: 18 Freq: 1594
Day of month: 19 Freq: 1593
Day of month: 20 Freq: 1601
Day of month: 21 Freq: 1593
Day of month: 22 Freq: 1601
Day of month: 23 Freq: 1594
Day of month: 24 Freq: 1596
Day of month: 25 Freq: 1594
Day of month: 26 Freq: 1593
Day of month: 27 Freq: 1601
Day of month: 28 Freq: 1593
Day of month: 29 Freq: 1499
Day of month: 30 Freq: 1461
Day of month: 31 Freq: 930


    The script is
   

#!/usr/bin/perl

@dom = ();
for ($year = 1066; $year <= 1996; $year++)
{
    open(CAL, "cal $year |");
    $row = <CAL>;                   # Get rid of year
    $row = <CAL>;                   # A blank line
    while($row = <CAL>)
    {
        for ($cols = 0; $cols < 3; $cols++)
        {
            $day = substr($row, 15 + ($cols * 23), 2);
            $dom[$day]++ if $day =~ m/^( |\d)\d$/;
        }
    }
    close(CAL);
}
for ($day = 1; $day <= 31; $day++)
{
    print "Day of month: $day Freq: $dom[$day]\n";
}
-- 
Russell Mosemann     Concordia College      Voice: (402) 643-7445
Computing Center     Seward, NE 68434       Fax:   (402) 643-4073
"If Teflon is non-stick, how do they get it to stick to the pan?"