[Haskell-cafe] cumulative sum

[Tamas K Papp]

Hi,

I have two lists, p and lambda (both are finite).  I would like to
calculate

1) the cumulative sum of lambda, ie if

lambda = [lambda1,lambda2,lambda3,...]

then

csum lambda = [lambda1,lambda1+lambda2,lambda1+lambda2+lambda3,...]

2) the cumulative sum of p*lambda (multiplication elementwise)

Once I know how to do the first, I know how to do the second I guess
(doing the multiplication using zipWith to get the p*lambda list, but
I would be interested in any other suggestions).  Currently I take and
sum, but then I am calculating the same sums many times.

Thanks,

Tamas