Iterators

• used consistently in builtin libraries
  • example: iterate through each member of an array:

    • array = ['a','b','c','d']
      array.each {|item| puts item }
      

• Making your own iterators: yield

  • def fibUpTo(max)
      i1,i2 = 1,1
      while i1 <= max
        yield i1
        i1,i2 = i2,i1+i2
      end
    end
    fibUpTo(100) {|f| print f, " "}
    #prints: 1 1 2 3 5 8 13 21 34 55 89