From: dempsejn@...
Date: 2002-01-05T11:41:08+09:00
Subject: [ruby-talk:30261] self being altered even when .dup'ed

Hey All,

I've just narrowed down something that was bugging me, and I think I'm 
realizing that its a feature, not a bug or error.
I'm extending chomp to take an array. here's the code:

class Array
 def tester
    v = self.dup
    p self
    p v
    v[0] = v[0].chomp
    v[1].chomp!
    p self
    p v    
  end

end

If you run that with:

a = ["str1\n","str2\n"]
a.tester

you'll see:

["str1\n", "str2\n"]
["str1\n", "str2\n"]
["str1\n", "str2"]
["str1", "str2"]

As I'd expect, the newline is gone from v[0] and v[1], but what bugs me 
is that its gone from self[1] as well...its clearly the chomp! call, 
but i'm a little confused...i thought .dup would make a copy that i'd 
play with leaving the original self alone...it would make sense to me 
if i did v = self, but i thought that's where the dupe would solve my 
problem...i could code the above slightly differently (using a simple 
chomp instead of chomp!) to get around this behavior, but i wanted to 
try and understand why its happening...
thanks!
Jack