From: Stephen Schor <beholdthepanda@...>
Date: 2008-04-15T22:41:15+09:00
Subject: Re: noob 'why doesn't this work' question

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sizeList = [0,1,2,3,4,5,6]
countarray = [3,4,6]
countarray.each {|x| sizeList.delete_at(x)}

Let's look at what's going on inside your .each block.
  The first iteration it will delete the sizeList[3].  ===> [0,1,2,4,5,6]
  The second iteration it will delete sizeList[4]  ===> [0,1,2,4,6]
  The final iteration it will delete sizeList[6]  ==> [0,1,2,4,6]   #there
is no sizeList[6] - deleteAt returns nil.

Your indexs are changing each time you call delete_at.

-Stephen





On Tue, Apr 15, 2008 at 9:15 AM, Robin Pedersen <robinpeder@gmail.com>
wrote:

> On Apr 14, 5:47 pm, Vincent Angeloni <nospam7...@mac.com> wrote:
> > Hi and greetings to all group members!
> >
> > I'm a new Ruby user with a background in Applescript, Hypertalk
> > (Supercard), and a little Unix. I was intrigued by Matt Neuburg's
> > article about Applescript and Ruby, and that's what got me reading some
> > intro books on Ruby. I just bought Textmate and I am lovin' it!
> >
> > Anyway, I am wondering why this seemingly simple script fails:
> >
> > sizeList = [0,1,2,3,4,5,6]
> > countarray = [3,4,6]
> > countarray.each {|x| sizeList.delete_at(x)}
> >
> > what I want to happen is that sizelist gets deleted at the positions
> > specified in countArray, but the result I am getting is:
> >
> > 0
> > 1
> > 2
> > 4
> > 6
> >
> > and the expected result should be 0,1,2,5, right?
> > What gives?
> >
> > TIA,
> > vince
> >
> > Mac OS X 10.5.2, G5 Quad, Textmate editor, ruby 1.86
>
> What about this:
>
> sizeList = [0,1,2,3,4,5,6]
> countarray = [3,4,6]
> countarray.sort.reverse.each {|x| sizeList.delete_at(x)}
>
> Result: 0,1,2,5
>
>

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