G'day all.
Quoting Robert Dockins
Edison's design hails from a time when MPTCs were not only non-standard (as they still are), but also not widely used, and before fundeps were avaliable (I think).
Yes. Chris Okasaki's original version of Edison was standard H98.
I've considered reformulating the Sequence class to be more similar to the Collection classes (which use MPTCs, fundeps and mention the element type),
The redesign of the Collection hierarchy was from my tree. The main reason why I changed it was that ternary tries couldn't really be typed properly. (Chris' implementation of Patricia trees used a phantom key type along with a stern warning to only define the Int instance. That didn't work for ternary tries, since the key type is polymorphic.) I didn't get around to fixing Sequence because there wasn't a need for it yet, but yes, it should be done. Cheers, Andrew Bromage