immutable-vs-mutatable.rb

myArray = [{:key => nil, :x => nil}, {:z => nil}, {:potato => "hi", :deep => {:deep => {:deep => "asf" } } } ]

print myArray
print "\n"
potato = "hi"

# IMMUTABLE VERSION: make a new array but with hashes that are either the same exact hash or an updated version
myArray2 = myArray.map do |hash|
  hash.key?(:key) ? hash.merge({:key => potato}) : hash
end

print myArray2

print "\n"

# MUTABLE VERSION: MMmake a new array for comparison but just mutate the hash if it has the key
myArray3 = []
myArray.each do |hash|
  if hash.key?(:key)
    hash[:key] = potato
  end
  myArray3.push(hash)
end

print myArray3

print "\n"
print myArray

# here we try compare whether the merged hashes are the same
myArray2.each_index do |idx|
  print "\n"
  print myArray2[idx].equal? myArray[idx] # can do a reference comparison that is O(1)
end

# here we try compare whether the mutated hashes are the same"
myArray3.each_index do |idx|
  print "\n"
  print myArray2[idx] == myArray[idx] # always returns true , would have to do a deep check
end

print "\n"