From: gotoken@... (GOTO Kentaro)
Date: 1999-10-30T05:31:40+09:00
Subject: [ruby-talk:00878] Re: local / dynamic variables

Hi, 

In message "[ruby-talk:00877] local / dynamic variables"
    on 99/10/29, ts <decoux@moulon.inra.fr> writes:

> This is probably a stupid question, but why in a block a variable is not
> always dynamic when this variable is defined between | |  ?
>
> i.e. :
>
> a = [1]; i = 0; a.each {|i| p i } # i is a local variable in the block
>                                   # at end it erase the previous value of i
> a = [1];        a.each {|i| p i } # i is a dynamic variable

As you see, in the formar case, |i| is shared with the outer scope.  
A significant use of this feature can be given:

  a = [4,5,6,3]
  sum = 0  
  a.each{|i| sum += i}
  p sum

In the book ``Object oriented scripting language Ruby'' (in Japanese), 
scopes of local variables are illustrated as follows:

foo = 25          #<-- scope of foo
                  #
class Foo         #
  bar = 55        # #<-- scope of bar
                  # #
  def baz(local1) # #
    local2 = 88   # # #<-- scope of local1,local2
                  # # #
    loop do       # # #
      local3 = 99 # # # #<-- scope of local3
      .....       # # # #
                  # # # #
    end           # # #
                  # # #
  end             # #
  .....           # #
end               #
.....             #

See also a related thread:
http://blade.nagaokaut.ac.jp/ruby/ruby-talk/thr200-403.html#root_351

p.s. Your question is not stupid but good :-)

-- gotoken