Ah, thanks very much! I missed those because I didn't see them as functions, and didn't think about expressions.
But then going back to my Q3, what is the point of the separate date_larger,int2smaller, etc. functions? Are they faster than least/greatest because they are specific to a particular data type?
Now to be a little more serious, if you want a single function to both support variadic number of arguments AND all of them in a single array, how could the function decide whether smallest(ARRAY[1,2,3]) shall return 1 or ARRAY[1,2,3] (which is the smallest out of all arguments)?
Personally I don't have any use cases where I'd be comparing arrays, and so would be happy to have a single array be treated as a list of elements. But I definitely see your point in more general terms!