The problem probably is that your Ord instance does not
define a total order. Below a small example exhibiting the
same problem.
This shows the usefulness of specification of Haskell programs
(e.g. with Programatica or HasCASL) - verification could be used to
detect such problems.
Till
module
Hello list. Are there situations where a set can contain duplicate
elements?
I have a newtype and it is an instance of 'Eq' via the 'compare' method,
and it is also an instance of 'Ord'. After some Data.Set operations
with sets of that type I get a set which contains two elements which
compare eq
