Factorial Case with Partial Applications

combination = -> (n) do
    ->(r) do
        n_factorial = 1
        r_factorial = 1
        n_r_factorial = 1
        for i in 0..n-1
            n_factorial*=(n-i)
        end
        for i in 0..r-1
            r_factorial*=(r-i)
        end
        for i in 0..(n-r)-1
            n_r_factorial*=((n-r)-i)
        end
        combinations = n_factorial/(r_factorial*(n_r_factorial))
        return combinations
    end
end
n = 10
r = 7
nCr = combination.(n)
puts nCr.(r)