From: ahoward <ahoward@...>
Date: 2003-01-31T01:02:14+09:00
Subject: Re: Local variables & blocks

On Thu, 30 Jan 2003, Martin DeMello wrote:

> But method-level scoping still works as before, so I don't see the problem.

module M

  SOME_INIT_LIST.each do |item|
    temp = M.method_a item
    M.method_b temp
  end

  # temp lives on in M's namespace !!!!!!!
end

include M

eval 'some code which may or may not set local var temp'

if defined temp
    # something very important, but will always run because module M writer
    # screwed up!!!!!!!!
end

> why would you want an instance variable to be scoped to a block?

i said 'object'.  you said '@object'.  i figured you had made a typo.  i meant
'object'.

> Pretty much, yeah. But in Ruby, with everything contained in methods and
> classes anyway, I tend not to bother so much about the global namespace.  If
> one had to distinguish by wa of keywords, I'd rather see a 'local' keyword
> than an 'export'.

this is _exactly_ the case with C.  can anyone here back me up that writing

  static int x;

_everywhere_ in library code, or more precisely _forgetting_ to do it, is a
_major_ headache!  just last week i was compiling some sources i did not write
into a wrapper libary, that author of the library stupidly had created a
method named 'alloc', NOT made it static, and NOT named it mypackage_alloc or
some such - you should have seen the error linking into c++ code...
automatically exported varables and contrary to the entire notion of OO
programing - one of the tenants being _encapsulation_, which i think extends
to more that just objects.  just earlier this week there was a thread about
people wrapping things properly in modules so importing libraries did not
pollute their namespace.

another thought i had was that automatically exporting every damn variable
must be a huge strain on the GC as well - for now it will now a reference to
every single object you create in a block will remain... how will they ever
get cleaned up?

-a

-- 

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