References: CLOSE (p 332), IN-PACKAGE (p 183), RENAME-PACKAGE (p 184),
TRACE (p 440), UNTRACE (p 440), INSPECT (p 442),
SET-SYNTAX-FROM-CHAR (p 361),
LOCALLY (p 156), PROVIDE (p 188), REQUIRE (P 188)
Related issues: REQUIRE-PATHNAME-DEFAULTS
Edit history: 26-Aug-88, Version 1 by Chapman
19-Sept-88, Version 2 by Chapman
6-Oct-88, Version 3 by Masinter
7-Oct-88, Version 4 by Masinter
26-Nov-88, Version 5 by Masinter
9-Dec-88, Version 6 by Masinter
The descriptions of CLOSE, IN-PACKAGE, RENAME-PACKAGE, TRACE, UNTRACE,
INSPECT, SET-SYNTAX-FROM-CHAR, LOCALLY, PROVIDE, and REQUIRE
are not clear about the values returned from those constructs.
Clarify that the return values for the listed constructs are as follows:
CLOSE -- T
IN-PACKAGE -- the new package, i.e. the value of *PACKAGE* after the
execution of IN-PACKAGE.
RENAME-PACKAGE -- the renamed package.
TRACE (when called with arguments) -- implementation-dependent.
UNTRACE -- implementation-dependent.
INSPECT -- implementation-dependent.
SET-SYNTAX-FROM-CHAR -- T
LOCALLY -- the return values of the last form of its body, i.e. the body is
surrounded by an implicit PROGN.
PROVIDE -- implementation-dependent.
REQUIRE -- implementation-dependent.
(NB: the issue CLOSED-STREAM-OPERATIONS proposes modifying
the return value of CLOSE on closed streams. The issue
REQUIRE-PATHNAME-DEFAULTS proposes removing
REQUIRE and PROVIDE. Those proposals would take
priority over this one.)
This clarification allows users to know when they can and can not
count on the values returned from these constructs.
Varies; the choices made here are consistent with many but
not all implementations.
Cost to Implementors:
This clarification will assist users in writing portable code.
Cost to users:
Small; it seems unlikely that there is much code that currently
depends on the return values of these functions; such code isn't
Specified is better than not, when it makes sense.
PROVIDE and REQUIRE are not likely to appear except in the "top level" of
files, and so their return value is possibly moot. Another proposal would
eliminate them from the language, and then their return value would definitely
There is some sentiment for leaving unspecified the values of the
debugging/environment features such as TRACE and UNTRACE,
for the same reasons that so much else of their behavior is unspecified.
Notes from Oct 88 X3J13:
Except for LOCALLY, why bother?
That just causes portability problems. Don't want to leave it
unspecified -unless- someone can cite a reason to do so.
"If many weren't defined, maybe we should leave 'em, but
since nearly all -are- defined, let's just go ahead and
round out the set."
Most text books she's seen show CLOSE returning NIL.
One text book shows it returning T.
Since some people like to think of T as success and NIL
as failure, maybe it should always return T.
(See Issue: CLOSED-STREAM-OPERATIONS.)