• Save file

def save(deck, filename) do
	binary = :erlang.term_to_binary(deck)
	File.write(filename, binary)
end

• Read file

File.read("{filename}")

# will return 
{:ok, <<....>>} # This is very common return type

# So, it's common 
{status, binary} = File.read("{filename}")

def load(filename) do
	{status, binary} = File.read(filename)
	:erlang.binary_to_term binary
end

# but, it doesn't treat error case, so below is recommended.

def load(filename) do
	{status, binary} = File.read(filename)

	# case is elixir-style, not if statement.
	case status do
		{:ok, binary} -> :erlang.binary_to_term binary
		{:error, _reason} -> "That file does not exist"
		# underscore means mentioning to compiler that I don't care this value. It's only for patter matching.
	end
end