From: Dark Ambient <sambient@...>
Date: 2006-07-03T22:59:24+09:00
Subject: Re: if problem in loop causing weirdness

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 <meshac.ruby@gmail.com> 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
>
>