class TEST_GCD
	--
	-- Have a look at feature `gcd' to have an example of assertions in a loop.
	-- Also note that SmartEiffel handle recursivity in assertions.
	-- (There is also a feature `gcd' in class INTEGER_GENERAL.)
	--

creation {ANY}
	make

feature {ANY}
	make is
		do
			check
				gcd(3, 4) = 1
				gcd(4, 4) = 4
				gcd(8, 4) = 4
				gcd(9, 8) = 1
				gcd(9, 12) = 3
			end
		end

	gcd (value_1, value_2: INTEGER): INTEGER is
			-- Great Common Divisor of `value_1' and `value_2'.
		require
			value_1 > 0
			value_2 > 0
		local
			value: INTEGER
		do
			from
				Result := value_1
				value := value_2
			invariant
				Result > 0
				value > 0
				gcd(Result, value) = gcd(value_1, value_2)
			variant
				Result.max(value)
			until
				Result = value
			loop
				if Result > value then
					Result := Result - value
				else
					value := value - Result
				end
			end
		ensure
			Result = gcd(value_2, value_1)
		end

end -- class TEST_GCD