# Something that can be cloned
#
# This interface introduces the `clone` method used to duplicate an instance
# Its specific semantic is left to the subclasses.
interface Cloneable
	# Duplicate `self`
	#
	# The specific semantic of this method is left to the subclasses;
	# Especially, if (and how) attributes are cloned (depth vs. shallow).
	#
	# As a rule of thumb, the principle of least astonishment should
	# be used to guide the semantic.
	#
	# Note that as the returned clone depends on the semantic,
	# the `==` method, if redefined, should ensure the equality
	# between an object and its clone.
	fun clone: SELF is abstract
end