CLHS: Issue PACKAGE-FUNCTION-CONSISTENCY Writeup

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## 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.

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