[Haskell-cafe] Computing sums

[Andrew Coppin]

Stephen Tetley wrote:
> Hi Andrew
>
> "Spot the difference"
>
> data Property x y = forall s. Property s (x -> s -> s) (s -> y)
> data Fold b c = forall a. F (a -> b -> a) a (a -> c)
>
>
> The later is from:
> http://squing.blogspot.com/2008/11/beautiful-folding.html
>
> Max Rabkin's is is closer to the original argument ordering of foldl.
>   

Hmm. So somebody else has come up with the exact same solution to the 
same problem.

My problem isn't exactly the same though. I'm interested in computing a 
"property" of a list, and recomputing it as elements are appended to the 
list. My "Property" structure provides an efficient way to do this, and 
to do so composibly. (E.g., if I want the maximum of the mean or 
something. Maximum and mean are both folds.)

PS. Epic, epic comment spam.