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bug in ruby


class Foo
  attr_accessor :bar

  def foo
    self.bar = 1

    if false
      bar = 2        # never executed
    end

    p self.bar       # prints 1
    p bar            # prints nil
  end
end

--
Posted via http://www.ruby-forum.com/.

Hi --

That's not a bug.  The parser sees:

   bar = 2

and that triggers the allocation of bar.  Since the expression is
inside of the if false block, it never gets executed, so bar is nil.

David

--
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    (See what readers are saying!  http://www.rubypal.com/r4rrevs.pdf)
Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
A. Ruby Power and Light, LLC (http://www.rubypal.com)

Sorry - where's the bug?  You think the

p bar

should give 1?  I believe you are thinking of

p @bar ??

Or have I - as I often do - missed the point? =)

sairam MP wrote:
>     if false
>       bar = 2        # never executed
>     end

There is no way that this conditional will be triggered.

if expr
  ...
end

will only execute the body of the if statement if expr is true. False is
never true (outside of politics), hence it is never executed.

This is a bug in your understanding of the language, not in the language
itself. You've not said exactly what you think it *should* do instead of
what it does, so it's hard to give an answer tailored to improving your
understandly.

But briefly: an assignment like "bar = 2" is seen at the time the program is
*parsed* and means that an unqualified "bar" is treated as a local variable
from that point onwards until the end of that scope. Whether or not it is
actually *executed* makes no difference.

When you write "self.bar" or "self.bar=" you are explicitly making a method
call to a method "bar" or "bar=" on the current object; this is never
treated as a local variable.

If you write "bar" by itself, this is treated as a method call on the
current object *unless* an assignment of the form "bar = x" has been seen by
the parser earlier in the scope.

Regards,

Brian.

--- sairam MP <sai@gmail.com> wrote:

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On 22.05.2007 14:53, Brian Candler wrote:

Additional reference material:

http://www.ruby-doc.org/docs/ProgrammingRuby/html/language.html#UO

Kind regards

        robert

On 5/22/07, sairam MP <sai@gmail.com> wrote:

[ snip ]

A gentle suggestion:

"Don't claim that you have found a bug"

http://www.catb.org/~esr/faqs/smart-questions.html#id270918

Robert Klemme schrieb:

It should be added in the documentation, that such an uninitialized local
variable is set to the initial value "nil".

Wolfgang Ndasi-Donner

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