# If problem in loop causing weirdness **URL:** \ **Category:** ruby-talk\ **Created:** [3 July 2006 12:24 UTC](https://rubytalk.org/t/if-problem-in-loop-causing-weirdness/28611 "2006-07-03T12:24:30Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Nuralanur](https://avatars.discourse-cdn.com/v4/letter/n/90db22/32.png) [@Nuralanur](https://rubytalk.org/u/Nuralanur)\ **Post date:** [3 July 2006 12:24 UTC](https://rubytalk.org/t/if-problem-in-loop-causing-weirdness/28611/1 "2006-07-03T12:24:30Z")
You can use the break command to stop iterating through a block, eg. (simplifying your commands a bit): file\_names=['a.txt','b.txt','c.txt'] file\_names.each do |x| if x=='b.txt' puts 'we already have ' + x + ' in that array ' break end end Best regards, Axel ---
**Author:** ![Dark\_Ambient](https://avatars.discourse-cdn.com/v4/letter/d/e9bcb4/32.png) [@Dark\_Ambient](https://rubytalk.org/u/Dark_Ambient)\ **Post date:** [3 July 2006 12:49 UTC](https://rubytalk.org/t/if-problem-in-loop-causing-weirdness/28611/2 "2006-07-03T12:49:31Z")
Break doesn't seem to be the solution. To jump ahead to the behaviour, when asked if I want to overwrite, if answer is no, then everything behaves properly. If yes, which is covered in the else portion following 'get', it asks me 4x (there are 5 files in the directory I'm using. I've tried 'break' in various places (where it might have made sense) but didn't seem to correct the behaviour. Stuart > **···** > > On 7/3/06, Nuralanur@aol.com \ wrote: > > > You can use the break command to stop iterating through a block, eg. > > (simplifying your commands a bit): > > > > file\_names=['a.txt','b.txt','c.txt'] > > file\_names.each do |x| > > if x=='b.txt' > > puts 'we already have ' + x + ' in that array ' > > break > > end > > > > Best regards, > > > > Axel ---
**Author:** ![Travis\_Michel](https://avatars.discourse-cdn.com/v4/letter/t/e47c2d/32.png) [@Travis\_Michel](https://rubytalk.org/u/Travis_Michel)\ **Post date:** [3 July 2006 13:34 UTC](https://rubytalk.org/t/if-problem-in-loop-causing-weirdness/28611/3 "2006-07-03T13:34:23Z")
I suspect that the problem is with the deletion from an array within a loop of that array. Solution: construct a different array such that =\> if ow != 'no' then new\_array.push(x); end; consider the following test. irb(main):013:0\> x = [1,2,3,4] =\> [1, 2, 3, 4] irb(main):014:0\> x.each { |ii| irb(main):015:1\* print "ii = #{ii}\n" irb(main):016:1\> print "x = #{x}\n" irb(main):017:1\> x.delete(ii) irb(main):018:1\> print "x now = #{x}\n" irb(main):019:1\> } ii = 1 x = 1234 x now = 234 ii = 3 x = 234 x now = 24 =\> [2, 4] While this does not demonstrate your issue persay, it does however illustrate a bug. ii never equals the value of the original second index, because the array's iterator does not go back a step on deletion. Hope this helps. -trav > **···** > > -- > p [151,40,154,157,166,145,40,162,165,142,171].collect { |ii| eval > '"\\'+ii.to\_s+'"' }.join ---
**Author:** ![Dark\_Ambient](https://avatars.discourse-cdn.com/v4/letter/d/e9bcb4/32.png) [@Dark\_Ambient](https://rubytalk.org/u/Dark_Ambient)\ **Post date:** [3 July 2006 13:59 UTC](https://rubytalk.org/t/if-problem-in-loop-causing-weirdness/28611/4 "2006-07-03T13:59:24Z")
I 'suspected' this as I had a similar issue (different behaviour) in my last previous thread. What I had to do to correct things is if 'yes', push into the new array AND still delete from former array, and if 'no', just delete from former/existing array. Weird I think(?) especially in regards to the 'no', but without the delete, it continues to loop on the gets. Reposting my code just to show what I've changed. Things are working correctly not (until at least I add the next function :)). Thank you for the help! destdir = Dir['C:/testfilesmoved/\*.\*']          newmove =          destdir.each do |name|            pics2bmoved.each do |x|               if File.exist?(name) && File.compare(x, name) == true               puts x + ' already exists'               puts 'Do you want to overwrite? "yes" or "no"?'               ow = gets.chomp.downcase               if ow == 'yes' \<======== corrected               newmove.push(x)               pics2bmoved.delete(x)                 else \<============= corrected.                   pics2bmoved.delete(x)                   puts 'okay, file will not be overwritten'               end # for if file.exist?           end # ow       end # end for pics2bmoved loop   end # end for destdir loop   puts     if newmove.empty?       puts 'There are no files to be moved'        else             puts 'The following files will be moved'             puts newmove     end # for pic2bmoved list > **···** > > -------------------------------------------------------------------------------------------------------------- > On 7/3/06, Travis Michel \ wrote: > > > I suspect that the problem is with the deletion from an array within a loop > > of that array. > > > > Solution: construct a different array such that =\> if ow != 'no' then > > new\_array.push(x); end; > > > > consider the following test. > > > > irb(main):013:0\> x = [1,2,3,4] > > =\> [1, 2, 3, 4] > > irb(main):014:0\> x.each { |ii| > > irb(main):015:1\* print "ii = #{ii}\n" > > irb(main):016:1\> print "x = #{x}\n" > > irb(main):017:1\> x.delete(ii) > > irb(main):018:1\> print "x now = #{x}\n" > > irb(main):019:1\> } > > ii = 1 > > x = 1234 > > x now = 234 > > ii = 3 > > x = 234 > > x now = 24 > > =\> [2, 4] > > > > While this does not demonstrate your issue persay, it does however > > illustrate a bug. ii never equals the value of the original second index, > > because the array's iterator does not go back a step on deletion. > > > > Hope this helps. > > > > -trav > > -- > > p [151,40,154,157,166,145,40,162,165,142,171].collect { |ii| eval > > '"\\'+ii.to\_s+'"' }.join ---
**Author:** ![Matthew\_Smillie](https://avatars.discourse-cdn.com/v4/letter/m/a88e4f/32.png) [@Matthew\_Smillie](https://rubytalk.org/u/Matthew_Smillie)\ **Post date:** [3 July 2006 14:22 UTC](https://rubytalk.org/t/if-problem-in-loop-causing-weirdness/28611/5 "2006-07-03T14:22:49Z")
Not to be negative, but I don't think things are actually working, at least not the way you think they should be. It seems to me that there's no reason you should have to delete entries from the pics2bmoved array in this code, unless pics2bmoved has incorrect data in it to begin with. For example, the following initial conditions give you similar behaviour to what you describe, and would be 'fixed' using delete, since that deletes all of the duplicate entries, but the \*real\* bug would be in the code which creates pics2bmoved: destdir = ["/foo/a.txt", "/foo/b.txt"] pics2bmoved = ["/bar/a.txt", "/bar/a.txt", "/bar/a.txt", "/bar/b.txt", "/bar/b.txt", "/bar/b.txt"] So, basically, I have a \*very\* strong hunch that the bug you're seeing here actually exists somewhere else and that you're curing the symptom and not the disease. You should be able to confirm this by checking the state of the pics2bmoved variable before starting the loop, possibly as follows: destdir = Dir['C:/testfilesmoved/\*.\*'] newmove = puts pics2bmoved # ADDED THIS destdir.each do |name|    pics2bmoved.each do |x| [...]    end end This is part of a two-part general strategy that will really help you when you're learning to program. The first part is to work out what you \*think\* should be happening all the way through the code. The second part is to confirm that it's \*actually\* happening the way you think. Using 'puts' as above is the dead-simple way to do it, which lets you manually check that what's going on matches what you expect. There are various ways to automate this sort of checking, but doing it manually is probably best at first. Following on from previous questions of yours, I'll also point out that you've got the ends of the if statements mislabelled again. Remember, the first one started is the \*last\* one ended. You've got the loops right, though. matthew smillie. > **···** > > On Jul 3, 2006, at 14:59, Dark Ambient wrote: > > > I 'suspected' this as I had a similar issue (different behaviour) in > > my last previous thread. > > > > What I had to do to correct things is if 'yes', push into the new > > array AND still delete from former array, and if 'no', just delete > > from former/existing array. Weird I think(?) especially in regards to > > the 'no', but without the delete, it continues to loop on the gets. > > Reposting my code just to show what I've changed. Things are working > > correctly not (until at least I add the next function :)). Thank you > > for the help! ---
**Author:** ![Dark\_Ambient](https://avatars.discourse-cdn.com/v4/letter/d/e9bcb4/32.png) [@Dark\_Ambient](https://rubytalk.org/u/Dark_Ambient)\ **Post date:** [3 July 2006 15:07 UTC](https://rubytalk.org/t/if-problem-in-loop-causing-weirdness/28611/6 "2006-07-03T15:07:24Z")
> Not to be negative Your not being negative, I'd rather not program then learn to program badly (fixing symptoms versus actual bug). Though I know there is plenty of commercial software out there that does....(well that's for another discussion) > puts pics2bmoved # ADDED THIS After inserting this line "I" got thrown for a loop 🙂 First , there are two sections to the program (so far). The first section loops through the directory asking the users if they want to move a file. If affirmative, that file gets pushed into the new array (empty till then) via push. The second section (after the pics2bmoved is created) is suppose to go through and see if any files will be overwritten, giving the user the choice to say yes or decline to overwrite. So, I think one problem is the destdir is continuing to loop even after pics2bmoved is exhauster. Or something like that :). Perhaps my next step would be to somehow combine both sections into one. > Following on from previous questions of yours, I'll also point out > that you've got the ends of the if statements mislabelled again. > Remember, the first one started is the \*last\* one ended. You've got > the loops right, though. Thought I corrected that in my own reply to my original post. Good news on the loops though. Is that considered progress ;)....nevermind. > matthew smillie. Stuart > **···** > > On 7/3/06, Matthew Smillie \ wrote: > > > On Jul 3, 2006, at 14:59, Dark Ambient wrote: ---
**Author:** ![Matthew\_Smillie](https://avatars.discourse-cdn.com/v4/letter/m/a88e4f/32.png) [@Matthew\_Smillie](https://rubytalk.org/u/Matthew_Smillie)\ **Post date:** [3 July 2006 15:27 UTC](https://rubytalk.org/t/if-problem-in-loop-causing-weirdness/28611/7 "2006-07-03T15:27:20Z")
> > puts pics2bmoved # ADDED THIS > > After inserting this line "I" got thrown for a loop 🙂 > First , there are two sections to the program (so far). The first > section loops through the directory asking the users if they want to > move a file. If affirmative, that file gets pushed into the new array > (empty till then) via push. The second section (after the pics2bmoved > is created) is suppose to go through and see if any files will be > overwritten, giving the user the choice to say yes or decline to > overwrite. That sounds like a good description of what you want. Now you need to make predictions of exactly what should happen, so you can be sure everything is working. For example, if you start with 'a', 'b', 'c', 'd', then you want to say 'y,n,y,n' to the 'move?' question, then you should end up with 'a', 'c' at the end of the first section. That's something you can easily verify. > So, I think one problem is the destdir is continuing to > loop even after pics2bmoved is exhauster. Or something like that :). > Perhaps my next step would be to somehow combine both sections into one. Hmm. This strikes me as a possible misunderstanding of how nested loops work. The inner loop (pics2bmoved.each in this case) is executed once for every element in the outer loop (destdir.each). In a simpler example: a = ['a', 'b', 'c'] b = [1, 2, 3] a.each do |letter|    b.each do |number|      puts "#{letter}, #{number}"    end end prints the following: a, 1 a, 2 a, 3 b, 1 b, 2 b, 3 c, 1 c, 2 c, 3 In other words, when you finish the inner loop, it does the next iteration of the outer loop, which restarts the inner loop again (and again...). Note that if you change the 'puts' to a push onto some array, you could end up with multiple copies of whatever you're pushing: a = ['a', 'b', 'c'] b = [1, 2, 3] c = a.each do |letter|    b.each do |number|      c.push(letter)    end end c =\> ['a', 'a', 'a', 'b', 'b', 'b', 'c', 'c', 'c'] Which seems similar to what I guessed your problem might be. Are you creating pics2bmoved in a similar sort of nested loop? Best of luck, matthew smillie. > **···** > > On Jul 3, 2006, at 16:07, Dark Ambient wrote: > > > On 7/3/06, Matthew Smillie \ wrote: ---
**Author:** ![Dark\_Ambient](https://avatars.discourse-cdn.com/v4/letter/d/e9bcb4/32.png) [@Dark\_Ambient](https://rubytalk.org/u/Dark_Ambient)\ **Post date:** [3 July 2006 16:23 UTC](https://rubytalk.org/t/if-problem-in-loop-causing-weirdness/28611/8 "2006-07-03T16:23:23Z")
> Hmm. This strikes me as a possible misunderstanding of how nested > loops work. The inner loop (pics2bmoved.each in this case) is > executed once for every element in the outer loop (destdir.each). In > a simpler example: > > a = ['a', 'b', 'c'] > b = [1, 2, 3] > a.each do |letter| >    b.each do |number| >      puts "#{letter}, #{number}" >    end > end > > prints the following: > a, 1 > a, 2 > a, 3 > b, 1 > b, 2 > b, 3 > c, 1 > c, 2 > c, 3 Excellent illustration, very helpful , though the results are still forthcoming. > Which seems similar to what I guessed your problem might be. Are you > creating pics2bmoved in a similar sort of nested loop? pics2bmoved was created using just .push (which was the first section) However in section 2, it was the inner loop to the destination directory / or outer array. This would explain the repeating for the same element. I've gone ahead and am attempting to condense the two sections into one. I'm still faced with the same loop issues though for now. > Best of luck, > matthew smillie. Stuart > **···** > > On 7/3/06, Matthew Smillie \ wrote: ---
**Author:** ![Dark\_Ambient](https://avatars.discourse-cdn.com/v4/letter/d/e9bcb4/32.png) [@Dark\_Ambient](https://rubytalk.org/u/Dark_Ambient)\ **Post date:** [3 July 2006 16:52 UTC](https://rubytalk.org/t/if-problem-in-loop-causing-weirdness/28611/9 "2006-07-03T16:52:47Z")
Condensed version: require 'ftools' Dir.chdir 'C:/testfilesmoved' require 'ftools' pic\_names = Dir['C:/testfilesorig/\*.\*'] destdir = Dir['C:/testfilesmoved/\*.\*'] pics2bmoved = pic\_names.each do |name|             puts 'Do you wish to move ' + name + 'file?,"yes" or "no" ?'                decision = gets.chomp.downcase                      if decision == 'yes'                           destdir.each do |x|                              if File.compare(name, x) == false                                 pics2bmoved.push(name)                                 # problem here, first with loop same as b4, so                                 # i removed the files from destdir, so File.compare wouldn't hit true                                 # yet, the pics2bmoved.push doesn't seem to work.                                 else                                     puts 'The file already exists in destination, overwrite? "yes" or "no" '                                         ow = gets.chomp.downcase                                  if ow == 'yes'                                      pics2bmoved.push(name)                                      else                                         puts 'This ' + name + ' will not be moved'                                  end # for ow==yes                            end # for File.compare                         end # for destdir loop                     end # for decision == yes        end # for pic\_names loop            if pics2bmoved.empty?                puts                puts 'No files will be moved'                      else                      puts pics2bmoved           end > **···** > > On 7/3/06, Dark Ambient \ wrote: > > > On 7/3/06, Matthew Smillie \ wrote: > > > > \> Hmm. This strikes me as a possible misunderstanding of how nested > > \> loops work. The inner loop (pics2bmoved.each in this case) is > > \> executed once for every element in the outer loop (destdir.each). In > > \> a simpler example: > > \> > > \> a = ['a', 'b', 'c'] > > \> b = [1, 2, 3] > > \> a.each do |letter| > > \> b.each do |number| > > \> puts "#{letter}, #{number}" > > \> end > > \> end > > \> > > \> prints the following: > > \> a, 1 > > \> a, 2 > > \> a, 3 > > \> b, 1 > > \> b, 2 > > \> b, 3 > > \> c, 1 > > \> c, 2 > > \> c, 3 > > > > Excellent illustration, very helpful , though the results are still forthcoming. > > > > \> Which seems similar to what I guessed your problem might be. Are you > > \> creating pics2bmoved in a similar sort of nested loop? > > > > pics2bmoved was created using just .push (which was the first section) > > However in section 2, it was the inner loop to the destination > > directory / or outer array. > > This would explain the repeating for the same element. I've gone > > ahead and am attempting to condense the two sections into one. I'm > > still faced with the same loop issues though for now. > > \> Best of luck, > > \> matthew smillie. > > > > Stuart ---
**Author:** ![Dark\_Ambient](https://avatars.discourse-cdn.com/v4/letter/d/e9bcb4/32.png) [@Dark\_Ambient](https://rubytalk.org/u/Dark_Ambient)\ **Post date:** [3 July 2006 18:44 UTC](https://rubytalk.org/t/if-problem-in-loop-causing-weirdness/28611/10 "2006-07-03T18:44:04Z")
Just wanted to finish the thread off here by saying I finally have working code, accomplishing my task of utilizing File.exists? and eliminating my loop issues. For the sake of my own self-aggrandizement I'll post the code (open to criticism or comment) Dir.chdir 'C:/testfilesmoved' require 'ftools' pic\_names = Dir['C:/testfilesorig/\*.\*'] destdir = Dir['C:/testfilesmoved/\*.\*'] pics2bmoved = [] pic\_names.each do |name|       puts 'Do you wish to move ' + name + 'file?,"yes" or "no" ?'       decision = gets.chomp.downcase                   if decision == 'yes'                     if destdir.empty?                       pics2bmoved.push(name)                       else                     if File.exists?(destdir[name.to\_i]) == false                         pics2bmoved.push(name)                         else                         puts name + ' already exists in destination, overwrite? "yes" or "no" '                         ow = gets.chomp.downcase                           if ow == 'yes'                            pics2bmoved.push(name)                             else                             puts 'This ' + name + ' will not be moved'                     end # ow == yes                   end # File.exists?                 end # destdir.empty?              end # decision == yes            end # for pic\_names loop                    if pics2bmoved.empty?                    puts                    puts 'No files will be moved'                    else                      puts                      puts 'These files will be moved'                      puts pics2bmoved                   end