step argument for count

[smichr at gmail.com]

Does anyone know why a step argument was left off of count? There must
be something that I am missing in why this is the case. For example, I
read that the negative start and step were left off of islice because
iterables can be of "infinite length" so you won't know apriori where
the end is. But how would you be using count in a way that *couldn't*
use a step argument?

/c