# Recursion help **URL:** \ **Category:** Ruby\ **Created:** [November 14, 2007, 10:59pm UTC](https://www.ruby-forum.com/t/recursion-help/120227 "2007-11-14T22:59:38Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![nuby2ruby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/54ee81/32.png) [@nuby2ruby](https://www.ruby-forum.com/u/nuby2ruby)\ **Post date:** [November 14, 2007, 10:59pm UTC](https://www.ruby-forum.com/t/recursion-help/120227/1 "2007-11-14T22:59:38Z")
I suck at recursion, and I need some help understanding where I’m going wrong here. I have a script that reads a file, then creates an excel form file. Here’s the program. puts “Enter file name” filename = gets.chomp puts “Enter carton size” carton\_size = gets.chomp out\_file = File.new(“C:/test/inner workings.xls”, “w+”) out\_file.write(“Carton number \t Carton quantity \t Card number \n”) file\_size = IO.readlines(filename).size total\_cartons = (file\_size.to\_f / carton\_size.to\_f).ceil i = 0 sequence = 1 in\_file = File.open(filename) unless in\_file.eof? (i…(carton\_size.to\_i - 1)).each do |number| record = in\_file.readline out\_file.write("#{sequence}\t#{total\_cartons}\t#{record[7, 19]} \n") end sequence += 1 if sequence \> total\_cartons break end end The problem I am running into, is it works fine until the sequence += 1 part. the output looks like 1 \t 7 \t 1234 1234 1234 1 \t 7 \t 1234 1234 1235 then right before 2 \t 7 \t 1234 1234 1300 it says “Done!” and closes. out\_file.close puts “Done!” I hope this makes sense enough for me to get some help. Thanks, ~Jeremy ---
**Author:** ![nuby2ruby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/54ee81/32.png) [@nuby2ruby](https://www.ruby-forum.com/u/nuby2ruby)\ **Post date:** [November 14, 2007, 11:07pm UTC](https://www.ruby-forum.com/t/recursion-help/120227/2 "2007-11-14T23:07:15Z")
Hi – On Thu, 15 Nov 2007, removed\_email\_address@domain.invalid wrote: > carton\_size = gets.chomp > > break > then right before > 2 \t 7 \t 1234 1234 1300 > it says “Done!” and closes. > > out\_file.close > puts “Done!” > > I hope this makes sense enough for me to get some help. Do you want ‘until’ instead of ‘unless’? David ---
**Author:** ![nuby2ruby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/54ee81/32.png) [@nuby2ruby](https://www.ruby-forum.com/u/nuby2ruby)\ **Post date:** [November 14, 2007, 11:37pm UTC](https://www.ruby-forum.com/t/recursion-help/120227/3 "2007-11-14T23:37:41Z")
David A. Black wrote: > Do you want ‘until’ instead of ‘unless’? Oh man, whoops! haha. Yes, I do want that. I must be tired or something to not catch something simple like that. Ok, well that presents a new problem, because I know when it hits the end of the file it will throw an error, but I will play with that and see what I come up with. Thanks. ~Jeremy ---
**Author:** ![nuby2ruby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/54ee81/32.png) [@nuby2ruby](https://www.ruby-forum.com/u/nuby2ruby)\ **Post date:** [November 15, 2007, 12:58am UTC](https://www.ruby-forum.com/t/recursion-help/120227/4 "2007-11-15T00:58:20Z")
Done! Works great, but I am always interested in seeing how it can be better. Less code, cleaner, faster sort of thing. Here it is, if anyone has any ideas on how I can make it better, please do tell. puts “Enter file name” filename = gets.chomp puts “Enter carton size” carton\_size = gets.chomp puts “Enter header description” description = gets.chomp out\_file = File.new(“C:/test/#{description}.xls”, “w+”) out\_file.write("#{description}\n") out\_file.write(“Carton number \t Carton quantity \t Card number \n”) file\_size = IO.readlines(filename).size total\_cartons = (file\_size.to\_f / carton\_size.to\_f).ceil i = 0 sequence = 1 in\_file = File.open(filename) until in\_file.eof? (i…(carton\_size.to\_i - 1)).each do |number| if in\_file.eof? in\_file.close out\_file.close puts “Done!” exit end record = in\_file.readline out\_file.write("#{sequence}\t#{total\_cartons}\t#{record[7, 19]} \n") end sequence += 1 end ---
**Author:** ![nuby2ruby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/54ee81/32.png) [@nuby2ruby](https://www.ruby-forum.com/u/nuby2ruby)\ **Post date:** [November 15, 2007, 7:14pm UTC](https://www.ruby-forum.com/t/recursion-help/120227/5 "2007-11-15T19:14:48Z")
removed\_email\_address@domain.invalid wrote: > Done! Works great, but I am always interested in seeing how it can be > better. Less code, cleaner, faster sort of thing. Here it is, if > anyone has any ideas on how I can make it better, please do tell. I’ll do my very best. > puts “Enter file name” > filename = gets.chomp > > puts “Enter carton size” > carton\_size = gets.chomp carton\_size = gets.to\_i > puts “Enter header description” > description = gets.chomp I generally prefer it if apps take such things as command line parameters instead of reading them from within. Makes scripting much less of a hassle. Also it just “flows” better when invoking the application. But I guess that’s a matter of preference. > out\_file = File.new(“C:/test/#{description}.xls”, “w+”) > File.open(“C:/test/#{description}.xls”, “w”) do |out\_file| > Btw: Why are you using “w+” instead of just “w”? > out\_file.write(“#{description}\n”) > out\_file.write(“Carton number \t Carton quantity \t Card number \n”) Replace write with puts and then leave out the \n at the end. > file\_size = IO.readlines(filename).size in\_file = File.readlines(filename) file\_size = in\_file.size > total\_cartons = (file\_size.to\_f / carton\_size.to\_f).ceil > i = 0 You never change i, so unless that’s a bug, you should leave out this line. > sequence = 1 Leave that out too. > in\_file = File.open(filename) This too, because we already defined in\_file above. > until in\_file.eof? > in\_file.each\_with\_index do |record, sequence| > (i…(carton\_size.to\_i - 1)).each do |number| Change i to 0 if you leave out i above. Also you can leave out the to\_i because we already called it above. > ``` > if in_file.eof? > in_file.close > out_file.close > puts "Done!" > exit > end > record = in_file.readline > > ``` You can leave all that out because we’re iterating with each now and out\_file is opened with open+block and as such doesn’t have to be closed (in\_file is now an array in memory and not actually an opened file, so it needs no closing either). > ``` > out_file.write("#{sequence}\t#{total_cartons}\t#{record[7, 19]} > > ``` > > \n") out\_file.puts “#{sequence+1}\t#{total\_cartons}\t#{record[7, 19]}” # We need the +1 because each\_with\_index starts counting at 0 while your original code counted from 1. > end > > sequence += 1 You don’t need this line anymore. > end plus one more end. Here’s my version of the code all in one place: [http://pastie.caboo.se/118428](http://pastie.caboo.se/118428) (untested) HTH, Sebastian ---
**Author:** ![nuby2ruby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/54ee81/32.png) [@nuby2ruby](https://www.ruby-forum.com/u/nuby2ruby)\ **Post date:** [November 16, 2007, 12:16am UTC](https://www.ruby-forum.com/t/recursion-help/120227/6 "2007-11-16T00:16:54Z")
oh, I thought it was just where you have an iteration inside another iteration or like nested loops or something. Hmm. Thanks for the help. I tried your version of the program. It seems to go into an endless loop, or just takes a REALLY long time. I stopped it after 30 seconds. Honestly, I don’t really understand a whole lot of this. I just kind of throw things together until they work, but I am getting a lot better at understanding, which is why I like to see if people can make my program better. I can then ask why they did the things they do. So, I see why you would use “w” and not “w+”, but why do you use the ARGV[0] ||? I know that ARGV is an array, but I don’t know what it is used for, or why you would use it instead of making your own array. Also, why would you assign the filename the user input _or_ ARGV[0]? The thing with the each\_with\_index is that the second record will have a sequence of 2, and it should have a sequence of 1. So sequence only goes up to the total carton size. It is a ?? of ?? cartons i.e. 1 of 12 - 12 of 12. This stuff gives me a good head start though, thanks for the information. ~Jeremy On Nov 15, 10:15 am, Sebastian H. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![nuby2ruby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/54ee81/32.png) [@nuby2ruby](https://www.ruby-forum.com/u/nuby2ruby)\ **Post date:** [November 15, 2007, 7:16pm UTC](https://www.ruby-forum.com/t/recursion-help/120227/7 "2007-11-15T19:16:34Z")
removed\_email\_address@domain.invalid wrote: > I suck at recursion, and I need some help understanding where I’m > going wrong here. You’re not using recursion at all in your code. Recursion is if a method invokes itself. ---
**Author:** ![nuby2ruby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/54ee81/32.png) [@nuby2ruby](https://www.ruby-forum.com/u/nuby2ruby)\ **Post date:** [November 16, 2007, 1:06am UTC](https://www.ruby-forum.com/t/recursion-help/120227/8 "2007-11-16T01:06:35Z")
removed\_email\_address@domain.invalid wrote: > oh, I thought it was just where you have an iteration inside another > iteration or like nested loops or something. Hmm. Thanks for the help. > “To understand recursion, one must first understand recursion.” Or alternatively, “To understand recursion, ask someone standing closer to Douglas Hofstadter to explain it.” 🙂 ---
**Author:** ![nuby2ruby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/54ee81/32.png) [@nuby2ruby](https://www.ruby-forum.com/u/nuby2ruby)\ **Post date:** [November 16, 2007, 9:12am UTC](https://www.ruby-forum.com/t/recursion-help/120227/9 "2007-11-16T09:12:56Z")
removed\_email\_address@domain.invalid wrote: > I tried your version of the program. It seems to go into an endless > loop, or just takes a REALLY long time. I stopped it after 30 > seconds. As I said, I didn’t test the code, but I really can’t see where it would go into an endless loop. I only have each-loops in there. If you give me a sample input file and a specification how the resulting output file should look like I could go and debug. > So, I see why you would use “w” and not “w+”, but why do you use the > ARGV[0] ||? As I said, I prefer command line arguments to reading from STDIN. ARGV[0]||ask\_for takes the first command line argument or, if there was no first command line argument, asks the user for input. > I know that ARGV is an array, but I don’t know what it is used for Command line arguments. > or > why you would use it instead of making your own array. Your own array would only contain elements you put in it. ARGV contains the command line arguments. > Also, why would > you assign the filename the user input _or_ ARGV[0]? So the script doesn’t ask for user input if the filename was already specified as a command line argument. > The thing with the each\_with\_index is that the second record will have > a sequence of 2, and it should have a sequence of 1. Your sequence variable started at 1, too, and was incremented by 1 at every iteration. The each\_with\_index with sequence+1 should behave exactly like that. HTH, Sebastian