Ruby yield and block and Iterators

The key word 'yield' is the core of Iterators, So I use a Iterators to clarify the 'yield'

class Sequence
        include Enumerable
        def initialize(from, to, by)
                @from, @to, @by = from, to, by
        end
        def each
                x = @from
                y = @by
                while x<= @to
                        yield x         #We will do something to the x, but not now, the operation will ensure in  the following block.
                        x += @by
                end
        end
end

We have use the 'yield' to possess the code line, but have not define the actual operationThen, we can use block to take the place!

s = Sequence.new(1, 10 , 2)
s.each {|a| print a}    #The |a| means use 'a' to alias the 'x''s place, then use 'print' to take the 'yield''s place

So the result is:13579

If we use bellow codes

s = Sequence.new(1, 10 , 2)
s.each {print 1}          #Nothing will alias to x, but the 'print 1' will take the 'yield''s place

So, the result would be:11111