On 06/30/2013 10:01 AM, Takashi Kato wrote:
> On 30/06/2013 17:47, Per Bothner wrote:
>> For an input/output port there are two positions - because there are
>> actually two separate ports.
> I disagree with this. It seems the point is mixed up with Java's problem
> and how port should be. IMO input/output port doesn't have to (or even
> must not) have two positions and it is one port.

No, the issue is not Java, but what a "port" conceptually is
(or should be): A "port" is a sequence of values, along with a current
position in that sequence.  An "input/output port" is not a sequence -
it is two sequences, along with two positions.

I.e. an input/output port is more naturally viewed as two distinct ports.
It is not in itself a port.  If you try to extend the concept of port to
include input/output ports then you no longer have a concept that has
that clean conceptual meaning.  Scheme should avoid such concepts.
--
	--Per Bothner
xxxxxx@bothner.com   http://per.bothner.com/