class Array
def each_from_both_sides
front_index = 0
back_index = self.length-1
while front_index <= back_index
yield self[front_index]
front_index += 1
if front_index <= back_index
yield self[back_index]
back_index -= 1
end
end
end
end
new_array = []
[1,2,3,4,5].each_from_both_sides { |x| new_array << x }
p new_array # => [1, 5, 2, 4, 3]