From: Ross Bamford <rossrt@...>
Date: 2006-04-13T01:42:36+09:00
Subject: Re: Simple substitutions

On Thu, 2006-04-13 at 00:24 +0900, Peter Bailey wrote:
>  I'm having a bit of 
> trouble though printing a simple array.length statement. Please check 
> this out:
> 
> ************************************************
> Dir.chdir('c:/scripts/ruby/temp')
> blanks = []
> File.read("test2.ps").scan(/\%\%Page: [\d()]+ 
> (\d{1,5})\n\%\%PageBoundingBox: \d{1,5} \d{1,5} \d{1,5} 
> \d{1,5}\n\%\%PageOrientation:/) do
>   blanks.push($1)
>   number = blanks.length
>   blanks.push(" ")
>   #break
> end
> 
> if blanks
>   File.open("psout2.txt", "w") { |out| out << "Blank Pages in This PDF: 
> #{blanks}\nNo. of Blanks: #number\n" }
> end
> ************************************************
> 
> 
> I'm getting this, which I'm extremely proud of, but, it doesn't quite 
> make it:
> 
> +++++++++++++++++++++++++++++++++++++++++
> Blank Pages in This PDF: 46 68 72 80 83
> No. of Blanks: #number
> +++++++++++++++++++++++++++++++++++++++++

You're almost there - I would make just a few small changes:

blanks = []
File.read("test2.ps").scan(/ ... your regexp ... /) do
  blanks.push($1)
end

unless blanks.empty?
  File.open("psout2.txt", "w") do |out|
    out << "Blank Pages in This PDF: #{blanks.join(' ')}\n" <<
	   "No. of blanks: #{blanks.length}\n"
  end
end

The key points I changed being:

	* Rather than having an extra " " in the array for each
	  element (which would throw the length off, too), I use
	  Array#join to format for output.

	* I surround all expressions within strings with #{} - 
	  prefixing with # alone works only for global variables
	  and is probably bad form - stick to #{var} as much as 
	  possible.

	* There's no need to have extra locals, e.g. 'number' in 
	  your code - you can make method calls in string expressions
	  and it's often more obvious what's going on.

	* I change 'if blanks' for 'unless blanks.empty?'. In Ruby,
	  everything apart from nil and false evaluate to true. This
	  includes empty arrays and zero.
	  
-- 
Ross Bamford - rosco@roscopeco.REMOVE.co.uk