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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 per@xxxxxxxxxxx http://per.bothner.com/