From: Mike Stok <mike@...>
Date: 2001-10-26T08:31:19+09:00
Subject: [ruby-talk:23378] Re: Unexpected results using File::SEPARATOR

On Fri, 26 Oct 2001, Paul Brannan wrote:

> I did something like this:
>
>   foo = File::SEPARATOR
>   foo << "foo"
>
>   bar = File::SEPARATOR
>   bar << "bar"
>
>   p foo, bar
>
> And I got this:
>
>   "/foobar"
>   "/foobar"
>
> This is not what I expected, but it makes sense, because I am modifing
> File::SEPARATOR.  Would it make sense to freeze File::SEPARATOR to keep
> this from happening?  With what other "constants" might this problem
> occur?

foo and bar refer to the same thing, maybe you want to make a copy of the
referent of File::SEPARATOR e.g.

[mike@ratdog mike]$ irb
irb(main):001:0> foo = File::SEPARATOR
"/"
irb(main):002:0> bar = File::SEPARATOR
"/"
irb(main):003:0> foo.equal?(bar)
true
irb(main):004:0> foo.id == bar.id
true
irb(main):005:0> foo == bar
true
irb(main):006:0> foo = File::SEPARATOR.dup
"/"
irb(main):007:0> bar = File::SEPARATOR.dup
"/"
irb(main):008:0> foo.equal?(bar)    # are the objects the same?
false
irb(main):009:0> foo == bar         # are the values in the objects the same?
true
irb(main):010:0> foo << 'foo'
"/foo"
irb(main):011:0> bar << 'bar'
"/bar"

You might want to look at the descriptions of dup and clone availabe at
http://www.rubycentral.com/book/ref_c_object.html and also the section on
Variables near the end of http://www.rubycentral.com/book/tut_classes.html
(in the book the diagram helps a little)

Hope this helps,

Mike

-- 
mike@stok.co.uk                    |           The "`Stok' disclaimers" apply.
http://www.stok.co.uk/~mike/       |
GPG PGP Key 1024D/059913DA         | Fingerprint      0570 71CD 6790 7C28 3D60
                                   |                  75D2 9EC4 C1C0 0599 13DA