Broadcast stream streams and echo-stream external format #820
Description
Current MAKE-BROADCAST-STREAM just checks that each of the target streams is a stream, causes an error only on a non-stream. It doesn’t check the access mode at broadcast-stream creation time, the error would be deferred until the first writing attempt.
Steele only says that the streams are streams. Is there some place a more detailed specification? Would it be an ill-advised departure from the standard to tighten this up?
That has nothing to do with external formats, just hygiene.
But there is another little question about echo streams and character operations. Steele says that every byte read on the input stream should be echoed on the output stream, i.e
(BIN echo) = (BOUT output (BIN input)).
That’s fine if the input and output streams have the same external format (modulo the fact that XCCS could be byte-inconsistent at that point in both streams). But what if the formats are different?
I would think that echoing should also be done at the higher character level:
(\INCCODE echo) = (\OUTCHAR output (\INCCODE input))
In that case the logical characters would be echoed, but the bytes wouldn’t be the same.
Obviously, they didn’t think of this. But is this the most sensible behavior in our more sophisticated world?