module Marshal: The marshaling library converts collections of Ruby objects into a byte stream, allowing them to be stored outside the currently active script. This d| docs.ruby-lang.org
module JSON: JavaScript \Object Notation (\JSON) \JSON is a lightweight data-interchange format. tt>.| docs.ruby-lang.org
class Symbol: A +Symbol+ object represents a named identifier inside the Ruby interpreter. literals.| docs.ruby-lang.org
class Rational: b (b>0), where a is the numerator and b is the denominator. mathematically.| docs.ruby-lang.org
class Complex: i>. en.| docs.ruby-lang.org