On Sun, Jan 19, 2020 at 9:57 PM Paul A Jungwirth <pj@illuminatedcomputing.com> wrote: > On Sun, Jan 19, 2020 at 4:38 PM Tom Lane <tgl@sss.pgh.pa.us> wrote: > > True for casts involving concrete types, mainly because we'd like > > the identity "value::typename == typename(value)" to hold without > > too much worry about whether the latter is a plain function call > > or a special case. Not sure whether it makes as much sense for > > polymorphics, since casting to a polymorphic type is pretty silly: > > we do seem to allow you to do that, but it's a no-op. > > > > ... > > > > Alternatively, consider this: a cast from some concrete multirange type > > to anymultirange is a no-op, while any other sort of cast probably ought > > to be casting to some particular concrete multirange type. That would > > line up with the existing operations for plain ranges. > > I agree you wouldn't actually cast by saying x::anymultirange, and the > casts we define are already concrete, so instead you'd say > x::int4multirange. But I think having a polymorphic function to > convert from an anyrange to an anymultirange is useful so you can > write generic functions. I can see how calling it "anymultirange" may > be preferring the implementor perspective over the user perspective > though, and how simply "multirange" would be more empathetic. I don't > mind taking that approach.
Here is a patch with anymultirange(anyrange) renamed to multirange(anyrange). I also rebased on the latest master, added documentation about the multirange(anyrange) function, and slightly adjusted the formatting of the range functions table.
I think so this patch is ready for commiter.
All tests passed, the doc is good enough (the chapter name "Range functions and Operators" should be renamed to "Range/multirange functions and Operators"
