From: Jim Weirich <jim@...>
Date: 2004-04-24T01:41:52+09:00
Subject: Re: attr_accessor vs. local variable


Kirk Haines said:
> On Sat, 24 Apr 2004, Jim Weirich wrote:
>> Kirk Haines said:
>> > This makes sense.  When you 'p x', all ruby knows about at that point
>> is
>> > the accessor method.
>>
>> Actually, by the time you execute 'p x', Ruby has already compiled the
>> method and knows that x is a local variable (since it saw an assignment
>> to
>> x).
>
> True.  It figures out the local variables at compile time (thus all the
> fun with eval and locals), but behaviorally, it seems like since the flow
> of execution has not reached the local variable declaration has not been
> reached yet, Ruby call the method x() instead.  Once the first assignment
> takes place, though, the local variable takes precedence over the method.
>
> It makes sense.  Am I misinterpretting what's happening?

I stand corrected.  References to 'x' that are lexically before the
assignment are treated as method calls.  References after the the
assignment are treated as local variables.  But notice it has nothing to
do with executeing the assignment.

That leads to the following example ...

$ cat x.rb
def x
  "METHOD CALL"
end
def f
  i = 2
  while i > 0
    puts x
    x = "LOCAL VARIABLE"
    puts x
    i -= 1
  end
end
f
$
$ ruby x.rb
METHOD CALL
LOCAL VARIABLE
METHOD CALL
LOCAL VARIABLE

-- 
-- Jim Weirich     jim@weirichhouse.org    http://onestepback.org
-----------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct,
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)