about as simple of a hash implementation as you could get

hash.rb

# concept of what a hash is doing internally
# This is intended for pedagogy, not actual use
# results will be nondeterministic, and sometimes not work correctly
class HashConcept
  
  KEY , VALUE = 0 , 1
  
  def initialize
    @hash_objects = Array.new 5
  end
  
  def []=(key,value)
    @hash_objects[index key] = [key,value]
  end
  
  def [](key)
    hashobj = @hash_objects[index key]
    return nil unless hashobj && hashobj[KEY] == key
    hashobj[VALUE]
  end
  
  def index(key)
    key.hash.abs % @hash_objects.size
  end
  
  def inspect
    @hash_objects.inspect
  end
  
end


my_hash = HashConcept.new

# can add and remove values based on a key
my_hash['a'] = 1
my_hash       # => [nil, nil, ["a", 1], nil, nil]
my_hash['a']  # => 1

# how did it know to store it in that index?
'a'.hash.abs % 5 # => 2

# can add more values
my_hash[12] = :my_fav_num
my_hash # => [[12, :my_fav_num], nil, ["a", 1], nil, nil]

# nonexistent keys return nil
my_hash[:not_a_real_key]  # => nil