From: Robert Klemme <shortcutter@...>
Date: 2010-04-01T16:52:43+09:00
Subject: Re: change in number of leading spaces

2010/4/1 Jesse B. <jessebos@aol.com>:
> Sorry about re-post due to typo.
>
> I am looping through a file and using a script that detects leading
> spaces (based on a previous post to this forum)
>
> What I want to do is to detect changes in number of leading spaces, for
> instance when one line has more, fewer, or the same number of leading
> spaces as the previous line.
>
> The problem I am having is with setting a value from within the loop
> which is then available on the next loop.
>
> here is an example of the program:
>
> infile = File.new("input.txt", "r")

You can simplify this by using

File.foreach "input.txt" do |line|
...
end

> outfile = File.new("output.txt", "w")

Also, please make it a habit to use the block form of File.open which
is much safer.  So this becomes

File.open("output.txt", "w") do |outfile|
...
end

For some background:
http://blog.rubybestpractices.com/posts/rklemme/001-Using_blocks_for_Robustness.html

> infile.each_line {
>  |i|
>
> spaces = i[/\A */].length
>
> #the following variable "stored" puts undef every time through, which
> means #it's not retaining the value on the next loop?
>
> if defined?(stored)== true
> puts stored

As Alex already pointed out this should be defined outside the loop.

Here's another variant

def count_leading_spaces(s)
  s[/\A */].length # or any other method that works
end

sp = 0

ARGF.each_line do |line|
  i = count_leading_spaces line

  if i != sp
    line.chomp! # avoid duplicate \n
    printf "Change from %2d to %2d spaces in this line %4d: %s\n",
      sp, i, ARGF.lineno, line
    sp = i
  end
end


Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/