Change in number of leading spaces

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”)
outfile = File.new(“output.txt”, “w”)
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

elsif defined?(stored)== nil
puts “undef”
stored = spaces
end

case spaces
when 1
output= “onespace”

when 2
output=“2 spaces”

end

outfile.write output
}

outfile.close()
infile.close()

outfile = File.new(“output.txt”, “r”)
outfile.each_line {
|i|
print “>>”, i
}

Your variable “stored” is only defined and used within the loop, so it
is local to the loop, and is lost when exiting the loop code block. You
need to either define it once outside the loop, before entering (stored
= nil), or make it an instance variable (@stored).

–Alex

2010/4/1 Jesse B. [email protected]:

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

Robert, Thank you for taking the time to write back.
I got the initial file operations you gave me working like so:

File.open(“output.txt”, “w”) do |outfile|
File.foreach “input.txt” do |line|
puts line
outfile.write line
end
end

which both displays the results on the command line and in the
output.txt file

then I tried to add in the rest like so

File.open(“output.txt”, “w”) do |outfile|
File.foreach “input.txt” do |line|

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

#puts line
#outfile.write line
end
end

and when I save as a ruby file and run from the command line nothing
happens, until i hit control-c and get a list of errors.

I think the problem is that I am incorrectly assembling your snippets.

Would it be possible to redo this as a complete example that works as a
ruby file run from the command line?

thank you in advance

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