+unless defined?(::JSON::JSON_LOADED) and ::JSON::JSON_LOADED
+ require 'json'
+end
+defined?(::Rational) or require 'rational'
+
+class Rational
+ def self.json_create(object)
+ Rational(object['n'], object['d'])
+ end
+
+ def as_json(*)
+ {
+ JSON.create_id => self.class.name,
+ 'n' => numerator,
+ 'd' => denominator,
+ }
+ end
+
+ def to_json(*)
+ as_json.to_json
+ end
+end