closure.rb

foo='foo'
bar='bar'

class A
  def self.call_block
    foo="I've got a lovely bunch of coconuts"
    bar='detitly doo'
    #note, yield calls the block assigned to a function
    yield foo, bar
  end
end

#this is our closure
#everything between do, end is our block
#this will print 'foobar' because 
#the block retains it's original scope,
#so foo='foo' rather than
#"I've got a lovely bunch of coconuts"
#even though it was reassigned in the function
A.call_block do 
  puts "foo+bar=#{foo}#{bar}"
end


#an example of passing parameters into a block
#a="I've got a lovely bunch of coconuts"
#b='detitly doo'
#because yield foo, bar passed the 
#*functions* local foo, bar into the block
#as parameters a,b
A.call_block do |a,b|
  puts a
  puts b
  puts foo
  puts bar
end