Iteratee interfaces?

[blake-regalia]

The callback parameters to some of the Dataset methods seem to be object interfaces that have named function members, test, map, and run. Was this a mistake, a limitation of WebIDL, or something else? To be clear, I believe the intent was to make these parameters function callbacks to align them with Array.prototype.* methods.
rdfjs/types#21

[bergos]

I wrote this aligned to the RDF Interfaces WebIDL. But I agree, it doesn't look right. I would be surprised if WebIDL doesn't cover this, so it's a mistake. We should find the correct WebIDL way of doing this and fix it.