[Rd] Suggestion: seek(..., rw="last") instead of seek(..., rw="")

[Henrik Bengtsson]

Hi.

In seek() the 'rw' argument takes three possible values, i.e. ""
(empty), "read", or "write" (partial matches allowed).

I was bitten by the meaning of "" when I in a loop used seek(con,
where=w) followed by a seek(con, where=w, rw="write").

I know that everything is (magically) in the help (?seek) and so was
the description of rw="": "File connections can be open for both
writing/appending, in which case R keeps separate positions for
reading and writing. Which 'seek' refers to can be set by its 'rw'
argument: the default is the last mode (reading or writing) which was
used."

However, may I suggest to change the default value to "last" (or
"recent" or similar) to make the effect of the default more explicit
(and only support "" for backward compatibility).

/Henrik