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Cleanup Issue `PACKAGE-FUNCTION-CONSISTENCY`

Category: CLARIFICATION/CHANGE
References: 11.7 Package System Functions and Variables (pp182-188)

Problem Description

CLtL is vague about whether either or both of package or package name are permissible in some cases.

Proposal (MORE-PERMISSIVE)

Clarify that it is permissible to pass either a package object or a package name (symbol or string) in the following situations: - the :USE argument to MAKE-PACKAGE or IN-PACKAGE - the first argument to IN-PACKAGE, FIND-PACKAGE, RENAME-PACKAGE or DELETE-PACKAGE - the second argument to INTERN, FIND-SYMBOL, UNINTERN - the second argument to EXPORT, UNEXPORT, IMPORT, SHADOWING-IMPORT, and SHADOW - the first argument (or a member of the list which is the first argument) to USE-PACKAGE or UNUSE-PACKAGE. - all package-name arguments in DEFPACKAGE except for the name and nicknames of the package being defined. - the first argument to PACKAGE-NAME, PACKAGE-NICKNAMES, PACKAGE-USE-LIST, or PACKAGE-USED-BY-LIST - the PACKAGE argument to DO-SYMBOLS. - the PACKAGE argument to DO-EXTERNAL-SYMBOLS. - the PACKAGE argument to DO-ALL-SYMBOLS.

If FIND-PACKAGE is given a package object as an argument, it simply returns it.

Clarify that the function MAKE-PACKAGE permits only a package name as an argument since it does not make sense to create an existing package.

Clarify that package nicknames must always be expressed as package names (symbols or strings) and may never be actual package objects.

In the list above, IN-PACKAGE may be changed to SELECT-PACKAGE if IN-PACKAGE-FUNCTIONALITY:NEW-MACRO passes.

Examples

  (INTERN "FOO" "KEYWORD") => :FOO

  (DEFVAR *FOO-PACKAGE* (MAKE-PACKAGE "FOO"))
  (RENAME-PACKAGE "FOO" "FOO0")
  (PACKAGE-NAME *FOO-PACKAGE*) => "FOO0"

(PACKAGE-NAME "SYS") might return "SYSTEM".

Rationale

This makes things more consistent. It also adds a generally useful capability.

Current Practice

Symbolics Genera & Lucid permit strings as package names. Symbolics Cloe does not permit strings as package names. In Lucid FIND-PACKAGE and IN-PACKAGE require names.

Cost to Implementors

Small.

Cost to Users

None. This change is upward compatible.

Cost of Non-Adoption

Implementations would continue to vary gratuitously, leaving a potential for portability problems.

Benefits

The cost of non-adoption is avoided.

Aesthetics

This makes things more regular, and so presumably more aesthetic.

Discussion

Pitman ran across this problem while trying to port Macsyma to various implementations. Discussion with other maintainers of portable programs shows this is a common source of aggravation in portable code.

It would be possible to say that MAKE-PACKAGE took package objects as arguments and just returned that package. That might have limited usefulness on rare occasions, but mostly seemed too far out in left field to bother suggesting it.

Edit History

21-Oct-88, Version 1 by Pitman
12-Jan-89, Version 2 by Masinter (add MORE-PERMISSIVE option)
17-Mar-89, Version 3, by Masinter, MORE-PERMISSIVE as
amended & adopted at Jan 89 X3j13
17-Mar-89, Version 4, by Moon, correct amended wording