Class: Numeric

Numeric is extended to expose a factorial method. For example:

 12.factorial

combinations_count factorial

Return the number of combinations of n (self) taken k at a time.

# File combinations.rb, line 92
        def combinations_count(k)
                self.factorial / (k.factorial * (self - k).factorial)
        end

# File factorial.rb, line 10
        def factorial
                (1..self).inject(1) {|prod,n| prod * n}
        end