From: Brian Candler <B.Candler@...>
Date: 2003-02-04T23:47:47+09:00
Subject: Re: Local variables & blocks

> Can someone list a synopsis of the new rules (or have I missed that?)
>  This thread got to be wayyyy too long to follow for me with all the
> points and counterpoints.

(1) Block parameters - e.g. |i,j| - are always local to the block,
regardless of whether a variable with the same name already exists. e.g.

  i = 0
  [1,2,3].each { |i|   # this is a *different* i (shadowing)
    puts i
  }
  puts i

will print 1 2 3 0

I think Matz wants a compulsory warning if you shadow a variable in this way
(i.e. generated even if you don't specify '-w')

(2) Other assignments are always bound to the method's main local variable
scope, whether or not it already exists. For example:

  [1,2,3].each { |i|
    j = i
  }
  puts j

will print '3', and

  [1,2,3].each { |i|
    j = i if i > 3
  }
  puts j

will print 'nil'. The same behaviour is achieved in the current version of
Ruby if you put 'j = nil' before the loop.

So two distinctions will no longer exist:

- block parameters are local or bound?
    => they are always local
- variables defined within a block are local or bound?
    => they are always bound

Under the current rules, in both cases they are 'bound' if an assignment to
a variable of the same name occured anywhere before the block, and 'local'
if not.

Regards,

Brian.