ruby each_line get the next line

Question

I have a file with some duplicate entries. It looks like

Los Angeles, 6
Los Angeles, 6 
New York, 31
New York, 31
New YOrk, 31
.
.
.

Now I want to get rid of the duplicate data. What I try to do is to use each_line, see if the line equals to the next line, if they are the same then just skip, and write to a new file. The problem is how should I get the next line of that file? Or any other suggestions to do this?

Answer 1

Comparing against the next line is unnecessary, since you can easily see if the current line matches the previous one:

file = File.open("filename", "r")
previous_line = nil
file.each_line { |line|
   if line == previous_line
     # duplicate line; ignore
   else
     # different; do whatever you want
   end

   # remember this line so we can compare against it
   previous_line = line
}