To: J3                                                     J3/24-101
From:      Steve Lionel
Subject:   F2023 interp: BOZ literals in interoperable enumerators
Date: 2023-December-18

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NUMBER: F23/013
TITLE: BOZ literals in interoperable enumerators
KEYWORDS: BOZ, enumerators
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:

For Fortran 2023, work item US-23 expanded the contexts in which
BOZ constants were allowed, to include "as the <initialization>
for a named constant of type INTEGER or REAL,..." (C7119).
19-256r1 had the primary edits, with 21-101 containing additional
edits not relevant to this paper.

19-256r1 contained examples showing use of BOZ constants in
PARAMETER statements, but did not mention interoperable
enumerators, which are "named integer constant[s]" (7.6.1p1).

Consider the following:

ENUMERATOR :: FOO = Z'123'

is this conforming in Fortran 2023? Clearly, the intent of US-23
was that it should be, but the syntax rule for <enumerator> is:

R762 enumerator is named-constant [ = scalar-int-constant-expr ]

Since a BOZ constant has no type (7.7p1), it can't be an integer,
and thus isn't a scalar-int-constant-expr. Was this exclusion
intended? (Note: PARAMETER does not have this issue.)

ANSWER:

No - it was intended to allow BOZ constants as the value for
interoperable enumerators just as they are in the PARAMETER
statement. Edits to correct this are provided.

EDITS to 24-007:

[7.6.1, 95:18+ Interoperable enumerations and enum types]

insert after:
R762 enumerator is named-constant [ = scalar-int-constant-expr ]

"               or <named-constant> [ = <boz-literal-constant> ]"

(The Editor is welcome to substitute an alternate expression of this
definition, such as creating a new term for the initializer.)

[7.6.1p6, 96:5-9 Interoperable enumerations and enum types]

In the numbered list following "The enumerator is a scalar named
constant, with the value determined as follows.", make the following
changes.

Insert after (1):
"(1a) if boz-literal-constant appears, the enumerator has the value
specified by INT(boz-literal-constant, C_INT), where C_INT is from
the intrinsic module ISO_C_BINDING."

In the current (2) and (3), replace "If scalar-int-constant-expr does
not appear" with "If neither scalar-int-constant-expr nor 
boz-literal-constant appears" such that the new list items read:

(2a) If neither scalar-int-constant-expr nor boz-literal-constant
appears and the enumerator is the first enumerator in enum-def, the
enumerator has the value zero.
(3a) If neither scalar-int-constant-expr nor boz-literal-constant
appears and the enumerator is not the first enumerator in enum-def,
it has the value obtained by adding one to the value of the
enumerator that immediately precedes it in the enum-def.

SUBMITTED BY: Steve Lionel

HISTORY: 24-101    m232  F23/013 submitted

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