Newbie question about quotation



Hi,

How does one create a function in maxima like "sum(-) " which
protects its first argument against premature evaluation?

More specifically suppose we have

ff(k):=if oddp(k) then 0 else 1

then ff(k) returns 1 (which I understand but consider somewhat
surprising) whereas
sum(ff(k),k,0,10) returns the correct value 6 (instead of 11).

How to duplicate this?

Michel