From: Colin Bartlett <colinb2r@...>
Date: 2010-06-02T12:52:44+09:00
Subject: Re: documentation mismatch ?

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This is (I believe) caused by a change in the (implicit) declaration and
scope of variables in Ruby 1.9.
In 1.9 variables in a block which are "similar" to parameters of methods
(that is |x| type variables) are local to that block. But in Ruby before 1.9
such variables are local to a block *unless* they are used/"declared" before
the block. I hope the following code run under Ruby_1.8.6 and Ruby_1.9.1
shows the difference.

"test-code.rb"
x = 355; y = 113
2.times do |x|
  puts "x inside the block: #{x}"
  y = 22; z = 7
end
puts "x outside the block: #{x}"
puts "y outside the block: #{y}"
puts "z outside the block: #{z}" rescue puts $!.inspect
x = 355; y = 113
2.times do |z|
  puts "z inside the block: #{z}"
  x = 33; y = 22
end
puts "x outside the block: #{x}"
puts "y outside the block: #{y}"
puts "z outside the block: #{z}" rescue puts $!.inspect

ruby 1.8.6 (2007-09-24 patchlevel 111) [i386-mswin32]
x inside the block: 0
x inside the block: 1
x outside the block: 1
y outside the block: 22
#<NameError: undefined local variable or method `z' for main:Object>
z inside the block: 0
z inside the block: 1
x outside the block: 33
y outside the block: 22
#<NameError: undefined local variable or method `z' for main:Object>

ruby 1.9.1p243 (2009-07-16 revision 24175) [i386-mingw32]
  running with warnings on gives:
test-code.rb:2 warning: shadowing outer local variable - x
x inside the block: 0
x inside the block: 1
x outside the block: 355
y outside the block: 22
#<NameError: undefined local variable or method `z' for main:Object>
z inside the block: 0
z inside the block: 1
x outside the block: 33
y outside the block: 22
#<NameError: undefined local variable or method `z' for main:Object>

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