On 8/7/06, Ahn, Ki Yung
I have posted an wiki article including one example of adding a counter to count the number of basic operations in sorting algorithm.
http://www.haskell.org/haskellwiki/Physical_equality
This was a rather simple situation and we figured out how to cure this by self equality check ( x==x ) forcing evaluation.
Forcing evaluation using (==) is a bit of a hack. Luckily, we have a better function to force evaluation: seq (which has type a -> b -> b). "seq x y" evaluates "x" to weak head normal form before returning "y". Let's try another feature of Haskell to force evaluation: strict data fields. A ! in front of a field in a data declaration signifies strictness. In the example below, whenever we construct a value with TT, the second argument is evaluated. \begin{code} data TT a b = TT a !b \end{code} Perhaps your instances will work correctly with this data declaration? Cheers, Spencer Janssen