Issue PACKAGE-FUNCTION-CONSISTENCY Writeup

Issue:        PACKAGE-FUNCTION-CONSISTENCY

References:   11.7 Package System Functions and Variables (pp182-188)

Category:     CLARIFICATION/CHANGE

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


Problem Description:


  CLtL is vague about whether either or both of package or package name

  are permissible in some cases.


Proposal (PACKAGE-FUNCTION-CONSISTENCY: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.