concept

main.rb

class X
	def self.concept name, &request
		impl_name = "#{name}_#{request}"
		alias_method impl_name, name
		@@concept_methods ||= {}
		@@concept_methods[name] ||= []
		@@concept_methods[name].unshift [request, impl_name]

		define_method(name){ |*args|
			for request, name_ in @@concept_methods[name]
				if request.(*args)
					return __send__ name_, *args
				end
			end
		}

		impl_name
	end

	def plus a, b
		p "plus by +"
		a + b
	end
	concept :plus do |a, b|
		a.class == b.class
	end

	def plus a, b
		p "plus by string"
		"#{a}#{b}"
	end
	concept :plus do |a, b|
		a.class == String && b.class == String
	end
end


p X.new.plus 1, 2
p X.new.plus "homu", "mami"