[R] multiple summation

[Paolo Bulla]

Hello,
I have to compute a multiple summation (not an integration because the 
independent variables a
are discrete) for all the values of a function of several variables f
(x_1,...,x_n), that is

sum ... sum f(x_1,...,x_n)
x_1     x_n

have you some suggestion? Is it possible?
I know that for multiple integration there is the function adapt, but it has at 
most n=20. In my case n depends on the dimension of the dataset and, hence, it 
could be bigger.

Thank you,
Paolo