get first and last row in one sql as two columns

Hi:

I need to get the first and last tow in one sql like below

select first(col1), last(col1) from table order by col1

I saw some posting in wiki with a custom function (or C extention)
to do this. Is it widely used and reliable?
https://wiki.postgresql.org/wiki/First/last_(aggregate)

I am wondering why these two functions are not part of postgresql built-in
functions as it has many use cases

Thanks