SUM or PROD function

[blankjul]

I am not sure how to implement a sum or a prod function that does iterate over a value.
For example: f(x) = sum(i, 1, 10, x^i)
Because the evaluation of the function is included in the sum, it is too late to use the current function implementation where the double[] is used as an argument.

Is there any other way to implement this?
Thanks in advance.

[boctulus]

Please, I'm also interested.