# Nesting Array loops **URL:** \ **Category:** Ruby\ **Created:** [April 9, 2007, 8:49am UTC](https://www.ruby-forum.com/t/nesting-array-loops/91442 "2007-04-09T08:49:07Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Rubic](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/ec9cab/32.png) [@Rubic](https://www.ruby-forum.com/u/Rubic)\ **Post date:** [April 9, 2007, 8:49am UTC](https://www.ruby-forum.com/t/nesting-array-loops/91442/1 "2007-04-09T08:49:07Z")
I new to Ruby and I have lost touch with whatever little programming I did know a few years back. Sorry if this is a lame question. How does one nest arrays? I want to check every element of the array and compare it against rest of the elements of that array for repeat occurences. but for now I did be happy if I can get to even print the 2 values, hence ‘puts #i, #j’ in the code. f = File.open(“iplist.txt”) f1 = File.open(“iplist.txt”) f.each { |i| f1.each { |j| puts “#{i}, #{j}” } } With the above code I only get output of one successful iteration of f.each and it stops and doesnt continue for the rest of the values of f.each. Surprisingly this works… (0…5).each { |i| (0…4).each { |j| puts “#{i}, #{j}” } } 00 01 02 03 04 05 10 11 12 …etc whats the difference between the codes thats causing this error? They are both arrays aint it? Thanks. 🙂 ---
**Author:** ![Rubic](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/ec9cab/32.png) [@Rubic](https://www.ruby-forum.com/u/Rubic)\ **Post date:** [April 9, 2007, 9:00am UTC](https://www.ruby-forum.com/t/nesting-array-loops/91442/2 "2007-04-09T09:00:08Z")
On Apr 9, 2007, at 2:49 AM, Rubic wrote: > ``` > f1.each { |j| > puts "#{i}, #{j}" > > ``` > > } > } Those aren’t arrays, they are files. You can’t assume that enumerable objects can be iterated more than once. You can reopen the file with each iteration or you can use File#rewind to ‘back up’ to the beginning of the file: f = File.open(“iplist.txt”) f.each { |i| File.open(“iplist.txt”) { |f1| f1.each { |j| puts “#{i.chomp}, #{j.chomp}” } } } f = File.open(“iplist.txt”) f1 = File.open(“iplist.txt”) f.each { |i| f1.each { |j| puts “#{i.chomp}, #{j.chomp}” } f1.rewind } ---
**Author:** ![Rubic](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/ec9cab/32.png) [@Rubic](https://www.ruby-forum.com/u/Rubic)\ **Post date:** [April 9, 2007, 9:16am UTC](https://www.ruby-forum.com/t/nesting-array-loops/91442/3 "2007-04-09T09:16:10Z")
Rubic wrote: > I new to Ruby and I have lost touch with whatever little programming I > did know a few years back. Sorry if this is a lame question. > > How does one nest arrays? One possibility: array = [[“foo”, “bar”], [“baz”, 42] ] > I want to check every element of the array and compare it against rest > of the elements of that array for repeat occurences. but for now I did > be happy if I can get to even print the 2 values, hence ‘puts #i, #j’ in > the code. > > f = File.open(“iplist.txt”) > irb(main):011:0\> f.class > =\> File > f1 = File.open(“iplist.txt”) > irb(main):011:0\> f1.class > =\> File > f.each { |i| > f1.each { |j| > puts “#{i}, #{j}” > } > } If you want an Array, use File#readlines. This produces an array of all lines in a file (including the \n at the end of each line), and you can iterate over them. For example: C:\>ruby test.rb line1,line1 line1,line2 line1,line3 line2,line1 line2,line2 line2,line3 line3,line1 line3,line2 line3,line3 C:\>cat test.rb #Create Arrays for the files: f = File.readlines(“test.txt”) f1 = File.readlines(“test.txt”) #Iterate over the Arrays: f.each do |i| f1.each do |j| puts “#{i.chomp},#{j.chomp}” end end > With the above code I only get output of one successful iteration of > f.each and it stops and doesnt continue for the rest of the values of > f.each. Probably because you have one big string in the file, and thus only one object the block can iterate. But without sample data, I can’t say more, really. > Surprisingly this works… > > (0…5).each { |i| > (0…4).each { |j| > puts “#{i}, #{j}” > } > } [snip] > whats the difference between the codes thats causing this error? They > are both arrays aint it? 0…5 and 0…4 are Ranges, not Arrays, and thus #each iterates over each element of the Range. – Phillip “CynicalRyan” Gawlowski [http://cynicalryan.110mb.com/](http://cynicalryan.110mb.com/) Rule of Open-Source Programming #7: Release early, release often. Clean compilation is optional. ---
**Author:** ![Rubic](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/ec9cab/32.png) [@Rubic](https://www.ruby-forum.com/u/Rubic)\ **Post date:** [April 9, 2007, 9:51am UTC](https://www.ruby-forum.com/t/nesting-array-loops/91442/4 "2007-04-09T09:51:11Z")
On Apr 9, 2007, at 2:49 AM, Rubic wrote: > f.each and it stops and doesnt continue for the rest of the values of > f.each. The problem is that both f and f1 are pointing to the same disk file. After the first iteration using f, the disk file is at EOF. When f1 attempts to iterate further, it sees the EOF and terminates. If you read the whole file into an array, your approach will work: ` f = File.read("/Users/mg/Desktop/test.txt") f = f.map { |e| e.chomp } # get rid on newlines puts f puts f.each do |i| f.each { |j| puts "#{i}, #{j}" } end ` quick fox brown fox quick, quick quick, fox quick, brown quick, fox fox, quick fox, fox fox, brown fox, fox brown, quick brown, fox brown, brown brown, fox fox, quick fox, fox fox, brown fox, fox However, to go back to your original problem of detecting duplicates, there are better ways. Here is one: ` # Array#uniq removes duplicates. def has_dups?(ary) ary.size != ary.uniq.size end f = File.read("/Users/mg/Desktop/test.txt") f = f.map { |e| e.chomp } # get rid on newlines has_dups?(f) # => true has_dups?(f.uniq) # => false ` Regards, Morton