ANSI Doc No: X3J16/93-0065
                                            ISO Doc No: WG21/N0272
                                                  Date: June 22, 1993
                                               Project: Programming Language C++
                                               Ref Doc:
                                              Reply To: Eric J. Krohn
                                                        krohn@bae.bellcore.com
                                                        +1 908 699-2708

                    Replacing Context Dependent Keywords by type-name



          1.  Abstract

          The C++ grammar in  the  working  paper  uses  context  dependent
          keywords  (18.1p1)  in  several  places.  These context dependent
          keywords are:  class-name,  enum-name,  and  typedef-name.   This
          paper  proposes  simplifying  the grammar by replacing these non-
          terminals with type-name where appropriate.


          2.  The Current Syntax

          The current grammar rules relevant to context dependent  keywords
          are shown in Appendix I.



          3.  Proposal 1 - Add missing type specifiers

          Studying the grammar reveals some deficiencies, namely:
             o enum-name is not valid as a type-specifier.
             o ::enum-name is not valid as a type-specifier.  In  fact,  no
               qualified form of enum-name is valid in type-specifier.
             o ::typedef-name  is  not  valid  as  a  simple-type-specifier
               (whereas ::class-name is).

          Making these changes affects the following rules:

             type-specifier:
                  simple-type-specifier
                  class-specifier
                  enum-specifier
                  elaborated-type-specifier
             DELETED   :: typedef-name
                  const
                  volatile
             qualified-enum-specifier:
                  enum-name
                  class-name :: qualified-enum-specifier
             simple-type-specifier:
                  qualified-class-specifier
                  ::(opt) qualified-type-specifier
                  ::(opt) qualified-enum-specifier









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                                                                 WG21/N0272

                  char
                  short
                  int
                  long
                  signed
                  unsigned
                  float
                  double
                  void




          4.  Proposal 2 - Consolidation with type-name

          The nonterminal class-name is specifically required before :: and
          after  ~  (destructors).   In  other  places, what matters is not
          whether a name is specifically a a typedef-name, or an enum-name,
          or a class-name but whether it is some kind of type name.  Hence,
          I propose substituting the  new  nonterminal  type-name  for  the
          other nonterminals wherever possible.

          Making these changes affects the following rules:

             type-name:
                  class-name
                  enum-name
                  typedef-name
             declarator-id:
                  id-expression
                  ~ class-name
                  qualified-type-name-specifier
             simple-type-specifier:
                  ::(opt) qualified-type-name-specifier
                  char
                  short
                  int
                  long
                  signed
                  unsigned
                  float
                  double
                  void

             DELETED   qualified-enum-specifier:
             DELETED        enum-name
             DELETED        class-name :: qualified-enum-specifier
             DELETED   qualified-type-specifier:
             DELETED        typedef-name
             DELETED        class-name :: qualified-type-specifier

             qualified-type-name-specifier:
                  type-name
                  class-name :: qualified-type-name-specifier









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                                                                 WG21/N0272
































































          June 22, 1993                Page 4                 X3J16/93-0065
                                                                 WG21/N0272



                         Appendix I - Original Grammar Rules


             class-name:
                  identifier
                  template-class-id
             enum-name:
                  identifier
             typedef-name:
                  identifier

             qualified-id:
                  nested-class-specifier :: id-expression
             type-specifier:
                  simple-type-specifier
                  class-specifier
                  enum-specifier
                  elaborated-type-specifier
                  :: typedef-name
                  const
                  volatile
             simple-type-specifier:
                  qualified-class-specifier
                  qualified-type-specifier
                  char
                  wchar_t
                  short
                  int
                  long
                  signed
                  unsigned
                  float
                  double
                  void
             qualified-type-specifier:
                  typedef-name
                  class-name :: qualified-type-specifier
             qualified-class-specifier:
                  nested-class-specifier
                   :: nested-class-specifier
             nested-class-specifier:
                  class-name
                  class-name :: nested-class-specifier
             declarator-id:
                  id-expression
                  qualified-type-specifier















          June 22, 1993                Page 5                 X3J16/93-0065
                                                                 WG21/N0272



                    Appendix II - Grammar Rules after Proposal 1


             class-name:
                  identifier
                  template-class-id
             enum-name:
                  identifier
             typedef-name:
                  identifier

             qualified-id:
                  nested-class-specifier :: id-expression
             type-specifier:
                  simple-type-specifier
                  class-specifier
                  enum-specifier
                  elaborated-type-specifier
             DELETED   :: typedef-name
                  const
                  volatile
             qualified-enum-specifier:
                  enum-name
                  class-name :: qualified-enum-specifier
             simple-type-specifier:
                  qualified-class-specifier
                  ::(opt) qualified-type-specifier
                  ::(opt) qualified-enum-specifier
                  char
                  short
                  int
                  long
                  signed
                  unsigned
                  float
                  double
                  void
             qualified-type-specifier:
                  typedef-name
                  class-name :: qualified-type-specifier
             qualified-class-specifier:
                  nested-class-specifier
                   :: nested-class-specifier
             nested-class-specifier:
                  class-name
                  class-name :: nested-class-specifier
             declarator-id:
                  id-expression
                  qualified-type-specifier












          June 22, 1993                Page 6                 X3J16/93-0065
                                                                 WG21/N0272



                    Appendix III - Grammar Rules after Proposal 2


             class-name:
                  identifier
                  template-class-id
             enum-name:
                  identifier
             typedef-name:
                  identifier
             type-name:
                  class-name
                  enum-name
                  typedef-name

             qualified-id:
                  nested-class-specifier :: id-expression
             type-specifier:
                  simple-type-specifier
                  class-specifier
                  enum-specifier
                  elaborated-type-specifier
             DELETED   :: typedef-name
                  const
                  volatile
             simple-type-specifier:
                  ::(opt) qualified-type-name-specifier
                  char
                  short
                  int
                  long
                  signed
                  unsigned
                  float
                  double
                  void
             qualified-class-specifier:
                  nested-class-specifier
                   :: nested-class-specifier
             qualified-type-name-specifier:
                  type-name
                  class-name :: qualified-type-name-specifier
             nested-class-specifier:
                  class-name
                  class-name :: nested-class-specifier
             declarator-id:
                  id-expression
                  ~ class-name
                  qualified-type-name-specifier