From: Mike Fletcher <lemurific+rforum@...>
Date: 2006-05-03T22:20:04+09:00
Subject: Re: Problem with MODULO function?

Peter Bailey wrote:
> The results of my little script here confuse me. I looking for an odd 
> number of pages in postscript files. When it's an odd number, I add a 
> blank, to make an even page count. In my test here, I've got 2 test 
> postscript files. One has 11 pages; the other has 42 pages. As can be 
> seen by my results below this script, it's seeing both as odd numbered, 
> and, it's adding a blank to each. Is my formula for MOD not correct? 
> I've tried it with "not equal to zero," like here, and, I've tried it 
> with "equal to one," with the same results.
> 
> Dir.chdir('c:/scripts/ruby/temp')
> psfiles = Dir.glob('*.ps')
> psfiles.each do |psfile|
>   File.open(psfile, "a") do |writepage|
>   	File.read(psfile).scan(/\%\%Pages: (\d{1,5})\n/) do
>   	  numberofpages = $1
>     	#Diagnostic to see the page counts of each file.
>     	puts numberofpages
>     	#If the page count is odd, then,
>           #add a blank to make it an even page count.
>     	if (numberofpages % 2) !=0 then
>       	#Diagnostic--what is it seeing?
>       	puts "odd number of pages"
>       	writepage << "showpage\n"
>     	end
>   	end
>   end
> end

The variable numberofpages contains a String instance, not a number. 
You're calling String#% which is the sprintf-like formatting operator, 
not Fixnum#% which is the modulo operator.  So "42" % 2 is the String 
"42", which is not going to be equal to numeric 0.

You want to convert the string to a number with

numberofpages = Integer( $1 )

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