Control Structures

     i = 0
     while i < 5
         puts i
         i = i + 1
     end

     i = 0
     until i >= 5
         puts i
         i = i + 1
     end

     for i in 1..4
         puts i
     end

     if i < 0
         puts "negative"
     elsif i == 0
         puts "0"
     else
         puts "positive"
     end