From: Matt Greer <matt.e.greer@...>
Date: 2007-07-21T04:22:25+09:00
Subject: Re: Is there a replacement for sub?

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On 7/20/07, Michael W. Ryder <_mwryder@worldnet.att.net> wrote:
>
>
> > a = "a b c d e f"
> > b = a
> > a = a.sub(" ", "") # => a is now "ab c d e f", b is still "a b c d e f"
> >
> Wrong.  Unless you use b = a.dup b will be the same as a as it is
> pointing to the same object.  The result of the sub operation will
> change b as well as a.


The original author was correct. b points to "a b c d e"
a gets replaced with "ab c d e" and b still points to the original string.

You're thinking something like

a = [1,3,4]
b = a
a[0] = 5

a and b are both [5,3,4]

irb(main):001:0> a = "a b c d e"
=> "a b c d e"
irb(main):002:0> b = a
=> "a b c d e"
irb(main):003:0> a = a.sub(" ", "")
=> "ab c d e"
irb(main):004:0> a
=> "ab c d e"
irb(main):005:0> b
=> "a b c d e"
irb(main):006:0>

Matt

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