Fri Oct 21 09:49:14 EDT 2011

Fold or Map

I've been trying to see for a while where the fold belongs.  The one
I'm using to fold (s -> i -> (s,o)) over [i] to produce [o].

The general form of this would be:

    (s -> i -> (s, o)) ->  (s -> f i -> (s, f o))

where f is a container type, i.e. lists.  In case f is infinite we
can't have the state output, so we get:

                       ->  (f i -> f o)

Note that for the processing code, f cannot be infinite and I really
do need the state output.

So.. what is this lift operation?