%!PS-Adobe-3.0
%%Pages: 1
%%EndComments
%
% ch-1-in-postscript.ps: translated ch-1.pl into Postscript.
%
% Yes, the language mostly used for printer page layout, can be used as a
% full-blown programming language.  However, you have to include functions
% to append strings and produce a variety of debugging messages down the
% page, before you start on the actual program logic.
%
% Debugging....

% const debuglm: left margin of debug messages
/debuglm 0.5 72 mul def

% const debugtop: top of debug messages - 11 inches up.
/debugtop 11 72 mul def

% const debugdown: how far to go down each line
/debugdown 20 def


% debugorigin():
%	 move to debugging origin
/debugorigin
{
	debuglm debugtop moveto
	(Debugging log:) show
	newline
} bind def


% debugn( name );
%	display a single string $name on a debug line.
/debugn
{
	30 0 rmoveto
	show		% show name
	newline
} bind def


% debugnv( name, value );
%	display name and value on a debug line.
%	keep this as it's so much simpler than debug() below
%	and also debug() has commented out invocations to
%	this throughout it:-)
/debugnv
{
	% initially: stack top: value, name
	30 0 rmoveto
	exch		% stack top: name, value
	show		% show name, stack top: value
	(: ) show
	50 string cvs show	% show convert_to_string(value)
	newline
} bind def


% debug( array_of_pairs );
%	display a single message, combining every pair of items (name,value)
%	in <array> as name: value, and comma-separating them.
%	eg debug( [(x) x (y) y (z) z] ) produces
%	"x: value_of_x, y: value_of_y, z: value_of_z"
%	(whether or not the values are strings or integers)
/debug
{
    6 dict begin	% next N items defined are in a local dictionary
	/array exch def % localize parameter name, removing it from stack
	/len 0 def	% local variable - length of array
	/pos 0 def	% local variable - position in array
	/name () def	% local variable - an array element
	/value () def	% local variable - next array element
	/first 1 def	% local variable - first time round loop?

	30 0 rmoveto

	/len array length def

	%Perl for pos = 0 to $#array step 2
	0 2 len 1 sub
	{
		/pos exch def

		%Perl $name = $array[$pos];
		/name array pos get def

		%Perl $value = $array[$pos+1];
		/value array pos 1 add get def

		%Perl print "," unless first
		first 0 eq {
			(, ) show
		} if

		%Perl print "$name: $value";
		name 50 string cvs show
		(: ) show
		value 50 string cvs show

		%Perl $first=0;
		/first 0 def
	} for

	newline

    end		% local dictionary destroyed here

} def


% newline();
%	go to left margin of next line for debug messages
/newline
{
	currentpoint debugdown sub % decrement Y pos
	exch pop		% drop old X
	debuglm exch		% form (debuglm,Y) on stack
	moveto			% go there!
} def


% result = append( string1, string2 )
% 	Concatenates two strings together.  Some languages
%	already know how to do stuff like this!!!
/append
{
	 % Initial stack: s1 s2 <-- top of stack
         2 copy		% s1 s2 s1 s2
	 length		% s1 s2 s1 len(s2)
	 exch		% s1 s2 len(s2) s1
	 length add	% s1 s2 len(s1)+len(s2)
         string dup     % s1 s2 r r
         4 2 roll       % r r s1 s2
         2 index	% r r s1 s2 r
	 0		% r r s1 s2 r 0
	 3 index	% r r s1 s2 r 0 s1
         putinterval    % strcpy( r+0, s1 )
         		% r r s1 s2
         exch		% r r s2 s1
	 length		% r r s2 len(s1)
	 exch		% r r len(s1) s2
	 putinterval	% strcpy( r+len(s1), s2 )
	 		% return r
} bind def


% isleap = isleapyear( y );
%	Return 1 if year $y is a leap year; 0 if not.
%
%Perl code:	return 0 if y % 4 != 0;
%Perl code:	return 1 if y % 100 != 0;
%Perl code:	return 0 if y % 400 != 0;
%Perl code:	return 1;
%
/isleapyear
{
    2 dict begin	% next N items defined are in a local dictionary
	/y exch def	% localize parameter name, removing it from stack
	/isleap 0 def	% local variable - the return value, boolean

	%[ (debug: is leap year y) y (isleap) isleap ] debug

	% if y%4 == 0 then
	y 4 mod 0 eq {          % 1st if..then
	     % if y%100 != 0 then isleap=1..
	     y 100 mod 0 ne {
		 /isleap 1 def
	% else  [y%100 == 0]
	} {
		 % isleap=1 if y%400 == 0
		 y 400 mod 0 eq {
		      /isleap 1 def
	         } if
	     } ifelse
	} if

	isleap		% leave result on stack

    end		% local dictionary destroyed here
} def


% dow = dayofweek1stjanyear( year );
%	Find and return the day-of-the-week
%	(0=Monday, 1=Tuesday.. 4=Friday, 5=Saturday, 6=Sunday)
%	of 1st Jan $year (only valid for year>=1900).
%
/dayofweek1stjanyear
{
    4 dict begin	% next N items defined are in a local dictionary
	/year exch def	% localize parameter name, removing it from stack
	/dow 0 def	% local variable: day-of-week, return value
			% why initial value 0?  1st Jan 1900 was Monday==0..
	/y 0 def	% local variable: for loop variable
	/days 0 def	% local variable: how many days to add (2 in leap years, 1 otherwise)

	% year--
	year 1 sub /year exch def

	% foreach my $y (1900..$year)
	% {
	1900 1 year
	{
		/y exch def
%		(y) y debugnv

		/days y isleapyear 1 add def
%		(days) days debugnv

%		%print "$y: advance $days days\n";
%		(y:) y 50 string cvs append (: advance ) append
%		days 50 string cvs append ( days) debugnv

		% dow = (dow + days) % 7;
		dow days add 7 mod /dow exch def

%		% print "dow=$dow"
%		(dow) dow debugnv
	% }
	} for

	dow	% leave value on stack

    end		% local dictionary destroyed here
} def


%
% mdays = daysinmonth( m, isleap );
%	Return the number of days in month $m (0..11), adjusting
%	number of days in February is $isleap is true.
%
/daysinmonth
{
    3 dict begin	% next N items defined are in a local dictionary
	/isleap exch def% parameter - boolean, are we in a leap year?
	/m exch def	% parameter - month number 0..11
	/d 0 def	% local variable

	%Perl my @d = (31,28,31,30,31,30,31,31,30,31,30,31);
	/d [31 28 31 30 31 30 31 31 30 31 30 31] def

	%Perl $d[1]=29  if $isleap;
	isleap 1 eq {
		d 1 29 put
	} if

	%Perl return $d[$m];
	d m get

    end		% local dictionary destroyed here
} def


% showweekdays( $y );
%	Show each month in year $y and the number of week days (Monday-Friday)
%	in that month.
%
/showweekdays
{
    8 dict begin	% next N items defined are in a local dictionary
	/y exch def	% parameter - the year
	/isleap 0 def	% local variable - boolean, is $y a leap year?
	/dow 0 def	% local variable - day-of-week: 0..6
	/m 0 def	% local variable - month: 0..11
	/mdays 0 def	% local variable - number of days in month $m
	/monthname 0 def% local variable - name of month $m
	/weekdays 0 def	% local variable - number of week days in month $m
	/d 0 def	% local variable - day number 1..$mdays

	%Perl my @monthname = qw(Jan Feb Mar Apr May Jun Jul
	%Perl			 Aug Sep Oct Nov Dec);
	/monthname [(Jan) (Feb) (Mar) (Apr) (May) (Jun) (Jul)
		    (Aug) (Sep) (Oct) (Nov) (Dec)] def

	%Perl my $isleap = isleapyear( $y );
	/isleap y isleapyear def

	%#Perl print "isleap[ $y ]: $isleap\n";
	%(isleap[ ) y 50 string cvs append ( ] ) append isleap debugnv

	%Perl my $dow = dayofweek1stjanyear( $y );
	/dow y dayofweek1stjanyear def

	%#Perl print "day-of-week[ 1st Jan $year ]: $dow\n";
	%(day-of-week[ 1st Jan ) y 50 string cvs append ( ] ) append dow debugnv

	%Perl foreach my $m (0..11)
	%Perl {
	0 1 11
	{
		/m exch def

		%Perl 	my $mdays = daysinmonth( $m, $isleap );
		/mdays m isleap daysinmonth def

		%Perl  my $mname = monthname[m];
		/mname monthname m get def
		%(monthname) mname debugnv

		%#Perl 	print "days in month[$mname, " $y]: $mdays\n";
		%(days in month[) mname append
		%( ) append
		%y 50 string cvs append
		%(]) append
		%mdays debugnv

		%Perl 	my $weekdays = 0;
		/weekdays 0 def

		%Perl 	foreach my $d (1..$mdays)
		%Perl 	{
		1 1 mdays
		{
			/d exch def
			%[ (d) d (dow) dow (weekdays) weekdays ] debug

			%Perl 		$weekdays++ if $dow < 5;
			dow 5 lt {
				weekdays 1 add /weekdays exch def
			} if

			% dow = (dow + 1) % 7;
			dow 1 add 7 mod /dow exch def

		%Perl 	}
		} for

		%Perl 	print "$mname $y: $weekdays weekdays\n";
		mname ( ) append
		y 50 string cvs append
		(: ) append
		weekdays 50 string cvs append
		( weekdays) append
		debugn

	%Perl }
	} for

    end		% local dictionary destroyed here
} def


%%Page: 1 1
%%PageOrientation: Portrait

/Helvetica-Bold findfont 13 scalefont setfont

debugorigin

2019 showweekdays

showpage