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Issue: ADJUST-ARRAY-NOT-ADJUSTABLE (Version 8)
- To: firstname.lastname@example.org
- Subject: Issue: ADJUST-ARRAY-NOT-ADJUSTABLE (Version 8)
- From: Jon L White <email@example.com>
- Date: Wed, 15 Mar 89 23:32:47 PST
- Cc: X3J13@Sail.stanford.edu
- In-reply-to: masinter.pa@Xerox.COM's message of 15 Mar 89 05:13 PST <890315-051405-3472@Xerox>
Although I haven't had time to join the overly-lengthy discussion on this
matter, I did point out one particularly confusing direction -- that this
proposal to "fix" the function ADJUST-ARRAY has become a proposal to alter
the semantics of the type SIMPLE-ARRAY. Compare CLtL, p28, with the
sentence in the Rationale Section:
"Specifying the points left unspecified (requiring all simple arrays to be
non-adjustable and all adjustable arrays to be non-simple) would require
large changes to some implementations and would be of little benefit to
and with an item in the Clarification section:
"a. Whether an array can be both simple and adjustable is unspecified."
[CLtL definition *does* specify it].
I suggested that a simple statement be added to the proposal as follows:
"This proposal does not attempt to alter the meaning of the type
SIMPLE-ARRAY in any way"
Moon expressed approval of adding that statement.
Altered semantics would mean that it is no longer a portable type. I
have sent out several trivially small examples that show this. Some
people have interpreted those examples as simply showing what happens
with "broken" code; but quite to the contrary, they show how code can be
"correct" on one implementation and "broken" on another ****** when the
definition of SIMPLE-ARRAY is allowed to vary between one implementation
and the other ******. Very carefully, CLtL spells out that implementations
may vary on the efficiency with which they implement SIMPLE-ARRAYS; but
nowhere does it provide for optional exclusion of some parts of the
Also, I note that all of the discussion on the Cl-cleanup list was by
persons other than the half-dozen or so maintainers of "stock hardware"
compilers. I personally spoke with three others (not including myself)
at Hawaii, and we all have identical requirements for the type SIMPLE-ARRAY,
and identical resolve that it must not be changed. Our compilers will
continue to offer this C-level optimization capability; the only
question is whether or not the CL1989 Standard will be cognizant of it.
-- JonL --