Demonstrate concepts of recursion and blocks

blocks_ex1.rb

class Array
  def my_map
    new_arr = []
    for el in self
      new_arr.push(yield(el))
    end
    new_arr
  end

  def my_map!
    ix = 0
    for el in self
      self[ix] = yield(el)
      ix += 1
    end
    self
  end
end

blocks_ex2.rb

class Hash

  def my_map
    new_hash = {}

    self.each do |k, v|
      new_hash[k] = yield(k, v)
    end
    new_hash
  end

  def my_map!
    self.each do |k,v|
      self[k] = yield(k, v)
    end
    self
  end
end

recursion_ex1.rb

def is_pal?(str)
  return true if str.strip.length <= 1
  str_array = str.scan(/\w/)
  str_next = str_array[1..-2].join
  return false unless str_array.first == str_array.last
  is_pal?(str_next)
end

is_pal?('racecar')