> I didn't see that claim in the linked slides, and it's not Haskell '98 (nor
> Haskell 2010).
 
I didn't realize it linked to the slides; I thought that pointed to the article. I just found another version of the paper, A Simple Implementation Technique for Priority Search Queues, by Hinze, which shows the binding type as a pair, with access functions for k and p. I'll continue to work my way through the material there. Thanks for you response.