From: Patrick Doyle <wpdster@...>
Date: 2008-09-20T02:06:45+09:00
Subject: That was unexpected -- strange scoping behavior

Consider the following piece of code:
#!/usr/bin/env ruby

def wow(idx, donetest)
  until donetest.call(idx)
    puts idx
    idx = idx + 1
  end #until
end #def wow

idx = 2
puts "before wow, idx = #{idx}\n"
wow(3, lambda {|x| x > 5})
puts "after wow, idx = #{idx}\n"

# Now, suppose I used a different dummy variable for the lambda function

puts "before wow, idx = #{idx}\n"
wow(3, lambda {|idx| idx > 5})
puts "after wow, idx = #{idx}\n"

---------------------------
When I just happened to use the name "idx" for my dummy variable in my
lambda function, I was quite surprised to learn that it changed the
value of "idx" in the enclosing scope.  I suppose that makes sense
(given Ruby's scoping rules), but it sure was unexpected!

--wpd