From: Gavin Sinclair <gsinclair@...>
Date: 2003-09-11T12:56:45+09:00
Subject: Re: What *are* variables? Which are nil now?

> [Hugh:]
>
>> Variables are not objects; it's as simple as that.  They are sticky
>> notes.  You can get a list of local variables in any scope with
>> Kernel::local_variables.  Then you can eval them to find out what they
>
> thanks, I missed that one.
>
>> are.
>>
>> You can get a list of variables in other scopes as well.  I have a
>> marvellous proof for this, which this margin is too small to contain.
>
> I seem to be needing large margins for my errors, I'll send you one! :-)
>  I'd like to know how to extract this info from Ruby.  It might not have
> helped in my case though, but would be generally good to
> have.
>

Heh, all I had in mind was this: if you can get a Binding to another
scope, then you can execute "local_variables" in that binding.  To wit:

  def foo
    a = 1
    b = 2
    c = 3
    return binding
  end

  b = foo                      # <Binding:0x10187e70>
  local_variables              # ["_", "b"]
  eval "local_variables", b    # ["a", "b", "c"]
  eval "a", b                  # 1
  eval "b", b                  # 2
  eval "b"                     # <Binding:0x10187e70>

I don't know if/how you can get a binding to another scope without
explicitly arranging it.  Not through Kernel::caller, for better or worse.

Gavin

# Now, who can tell me what that "_" local variable is?  Extra points for
# telling me why I should have known all along.