On Wed, Apr 18, 2007 at 01:47:04AM +0100, Neil Mitchell wrote: > >- If we permit undecidable instances, one may assign numerals to > >types. This gives us total order and hence comparison on types. > >In this approach, we only need N instances to cover N types. This is > >still better than Typeable because the equality is decided and can be > >acted upon at compile time. > > In my particular case whether I act at compile time or run time is > unimportant, but obviously this is an important advantage in general. > Unfortunately a cost of one instance per type is still higher than I'd > like to pay :-)
Now, it requires one line of code: {-# OPTIONS_DERIVE --derive=TTypeable #-} Stefan _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe