# ordinary/accumulator recursion

**Ketil Malde
**
ketil@ii.uib.no

*10 Sep 2001 09:50:35 +0200*

"Randles" <srandles@bigpond.net.au> writes:
>* Hi, Im a computer science undergraduate and we are studying haskell
*>* as part of our course. I have a question on recursion that i'd like
*>* to receive some sort of answer to.
*
Are you a tutor, then, since you'd like to receive answers, rather
than working them out yourself?
>* The question is to write a function to sum the first n terms in the series:
*
>* 1/1 + 1/3 + 1/5+ .. + 1/(2n-1)
*
>* using ordinary recursion and then using accumulator recursion.
*
I can think of several ways. For instance, given n as a parameter,
work out the nth term, and make a recursive call thus calculating the
sequence in reverse.
This should be fairly easy to extend with an accumulator, too.
You might get bonus points if you write a function using sum, take,
and map (hint: [1,3..]), or even generate an infinite list of
successive partial sums, and use (!!n) for the result.
>* Please help!
*
But of course!
-kzm
--
If I haven't seen further, it is by standing in the footprints of giants