Formal comment #223 (enhancement)

allow port position to be "magic cookie"
Reported by: 	Per Bothner
Version: 	5.92

port-position and set-port-position! are specified to get/set the
port's current position as a byte offset. But there are many kinds of
ports which do have a position, and on which the position can be
changed, but not using a byte offset. This includes most text ports
(except those implemented using simple stateless transcoders). In some
cases a character offset may make more sense.

Suggestion: For non-binary ports allow the use of any arbitrary
integral "magic cookie" as the position. One could also allow an
arbitrary value (such as a record), though that reduces the
"typeability" of these procedures. However, that would allow a
straight-forward wrapping of C's fgetpos/fsetpos.


RESPONSE:

The next draft will allow the use of integers to indicate
port positions, without requiring those integers to correspond
to byte offsets.  The editors will also consider the comment's
suggestion to allow non-integral positions, but have not yet
made a decision on that issue.