To: J3                                                     J3/22-114
From: Van Snyder
Subject: First Enumerator in an enumeration type should allow a value.
Date: 2022-February-03
Reference: 22-007

Comments on 7.6.2 Enumeration types
===================================

If should be allowed to specify a numeric constant value for the first
enumerator in an enumeration type. Thereby, enumerators can be used as
subscripts in dimensions whose lower bounds are not 1.  The description
of the limits for the argument for the type constructor (7.6.2p5), the
effect of input/output editing (13.7.2.2p6), and the value of the INT
intrinsic function (16.9.110), would need to be revised. TINY would need
to be defined for enumeration-type values, and its value would need to
be the first enumerator of the type. Thereby, one could write

  enumeration type :: T
    ....
  type(t) :: E
    ....
  integer :: X(tiny(e):huge(e))
    ....
  print *, x(e)

Is there a technical reason that an access-spec is not allowed on an
ENUMERATOR statement? The obvious semantics would be that it overrides
the access-spec on the ENUMERATION statement, and applies to all the
enumerators declared in that statement. For consistency with other
entities that can have an access-spec in their declarations, appearance
of their name in an access-stmt prevails.

Enumeration types should be extensible, but that can be added compatibly
in a later revision.

Input/output of enumeration-type objects should use their local names,
not their integer values. This can be added compatibly in a future
revision, using the A edit descriptor.

There seems to be no reason that enumeration-type namelist group objects
are probibited. Did J3 just run out of time to define it?

There seems to be no reason that list directed input/output is
prohibited for enumeration-type variables. Did J3 just run out of
time to define it?

Proposed edits
==============

Numeric value of first enumerator
---------------------------------

[91:11 R768 7.6.2 Enumeration types] Replace "<enumerator-name-list>" with
"<enumerator-name> [= <scalar-int-constant-expr>] [, <enumerator-name>
] ..."

[91:11+ R768+ 7.6.2 Enumeration types] Insert a constraint
"C7114a (R768) The <scalar-int-constant-expr> may appear only in the
        declaration of the first enumerator of the type."

[91:19 7.6.2p3 Enumeration types] Replace "ordinal position" with
"numeric value". Append a sentence "If <scalar-int-constant-expr> does
not appear in the declaration of the first enumerator of the type, its
numeric value is 1; otherwise, its numeric value is the value of
<scalar-int-constant-expr>. The numeric value of each successive
enumerator is one more than the numeric value of the preceding
enumerator."

[91:26-28 7.6.2p5 Enumeration types] Replace the paragraph:

"An enumeration constructor returns the value of the object of
enumeration type whose numeric value is the value of the
scalar-int-expr. The scalar-int-expr shall have a value that is greater
than or equal to the numeric value of the first enumerator of the type,
and less than or equal to the numeric value of the last enumerator of
the type."

[162:18 10.1.5.5.1p9 Interpretation of relational intrinsic operations]
Replace "ordinal" with "numeric". [Here, "ordinal position" (not
"ordinal value") would continue to work. But it would be the only place
where "ordinal" appears.]

[278:4-6 13.7.2.2p6 Integer editing] Replace "ordinal position" with
"numeric value" twice, in the first and last sentences. Replace
"positive and less than or equal to the number of enumerators" with "the
numeric value of an enumerator of the type of the input item".

[404:6 16.9.110p6 INT] Replace "ordinal position" with "numeric value".

Access-spec for enumerators
---------------------------

[91:11 R768 7.6.2 Enumeration types] Replace "[ :: ]" with "[ [ ,
<access-spec> ] :: ]"

[91:16 7.6.2p2 Enumeration types] After "enumerators" insert "The
<access-spec> on an ENUMERATOR statement specifies the accessibility of
each <enumerator-name> declared by that statement, and overrides any
default accessibility specified by an <access-spec> in the ENUMERATION
TYPE statement."