# Implementation of `to_s` for `Derivable` objects.
#
# The implementation uses `to_s` for each value of `attributes_to_map`.
#
# ~~~
# class A
#    auto_derive
#    super DeriveToS
#    var an_int: Int
#    var a_string: String
# end
#
# var a = new A(5, "five")
# assert a.to_s == "an_int:5; a_string:five"
# ~~~
#
# Warning: the method may go in an infinite recursion if there is a circuit in
# the implementation of `to_s`.
interface DeriveToS
	super Derivable
	redef fun to_s do return derive_to_map.join("; ", ":")
end