On 9 Apr 2008, at 17:49, Henning Thielemann wrote:
Also (2*5 == 7) would surprise people, if (*) is the symbol for a general group operation, and we want to use it for the additive group of integers.
One might resolve the "Num" binding of (+) problem by putting all operators into an implicit superclass: Roughly, let T be the set of of most general types, and for each t in T define a mangling string s(t). Then if the operator <op> :: t is defined somewhere, it is internally defined as class Operator_s(t)_<op> t where <op> :: t Then usages of it get implicit class (Operator_s(t)_<op> t, ...) => <Class> where ... and instance Operator_s(t)_<op> t where ... If I now have another class using (+), it need not be derived from Num, as both usages are derivable from an internal class Operator_(+) The mangling of the type via s(t) might be used to generate C++ style name overloading. It will then depend on how much ambiguity one wants to accept in the context. I do not see exactly how this works with Haskell current syntax; just an input. Hans