[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Proposal: count

Taylor R Campbell wrote:
   Date: Sun, 20 Sep 2009 18:58:38 -0400
   From: David Van Horn <dvanhorn@xxxxxxxxxxx>

While `length' gives you number of pairs in a list, it's also useful to determine the number of pairs in a (potentially) improper list.

When might one want to do this?

It's useful for bounds checking. Actually, I think a more useful operation would be something like:

   (lenth<=? obj k) -> bool

Which would be the same as (<= (count obj) k). This operation would take O(min(log(count obj),log k)). It's important to note that obj need not be a list.