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Issue: DRIBBLE-TECHNIQUE (Version 1)
- To: CL-Cleanup@SAIL.STANFORD.EDU
- Subject: Issue: DRIBBLE-TECHNIQUE (Version 1)
- From: Kent M Pitman <KMP@STONY-BROOK.SCRC.Symbolics.COM>
- Date: Sun, 6 Dec 87 17:13 EST
- Cc: KMP@STONY-BROOK.SCRC.Symbolics.COM
References: DRIBBLE (p443)
Edit history: 06-Dec-87, Version 1 by Pitman
Status: For Internal Discussion
The intent and effect of DRIBBLE is not very clearly specified.
Clarify that DRIBBLE is intended primarily for interactive debugging
and that its effect cannot be relied upon from programs.
#1: (PROGN (DRIBBLE "temp")
#2: (DRIBBLE "temp")
(PROGN (PRINT 'FOO)
Users of DRIBBLE have been surprised about how differently DRIBBLE
behaves in different implementations. This makes the status quo
much more explicit and will lead to less surprise.
Some implementations implement DRIBBLE as a function which simply
assigns streams such as *STANDARD-OUTPUT* to broadcast streams
(or the approximate equivalent thereof). Even within this camp,
there is not widespread agreement about which streams are affected.
However, typically test case #1 will capture the output of (PRINT 'FOO)
in the file "temp" and will execute (PRINT 'BAR) but not capture its
Some implementations (eg, Symbolics) push to a recursive command
loop when DRIBBLE is called with an argument, and return from that
command loop when DRIBBLE is called with no argument. In these
implementations, test case #1 will enter a recursive command loop
upon the first call to DRIBBLE and will not execute the (PRINT 'FOO)
until (DRIBBLE) is done interactively. When the second (DRIBBLE)
in test case #1 is executed, DRIBBLE will complain that output is
not currently being recorded. In test case #2, the output of
(PRINT 'FOO) will be captured, but the form (PRINT 'BAR) will never
be executed because (DRIBBLE) does not return normally (it throws).
None. This is just a clarification.
Users will be aware that they cannot rely on DRIBBLE in portable code.
Effectively none. Anyone who currently uses DRIBBLE in code that is
believed to be portable is kidding himself. If such code works in some
implementations, it can continue to work.
Since this is a clarification, there is no significant change to
Pitman wrote this proposal as a straw man so that CL-Cleanup would have
the issue on the books for explicit discussion.