Version 1.2 of ai22s/ai22-0008-1.txt

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!standard 4.3.3(14.1/5)          22-01-12 AI22-0008-1/02
!class binding interpretation 21-11-11
!status work item 21-11-11
!priority Low
!difficulty Easy
!qualifier Omission
!subject Nominal subtype of a delta aggregate
!summary
We talk about an applicable index constraint rather than a nominal subtype for a delta aggregate. Specifically, the base expression of a delta aggregate has the same applicable index constraint as the delta aggregate as a whole.
!question
4.3.3(14.1/5) says
For the base_expression of a delta_aggregate, if the nominal subtype of the delta_aggregate is a constrained array subtype, the applicable index constraint is the constraint of the subtype;
Does a delta aggregate have a nominal subtype? (No.)
!recommendation
(See Summary.)
!wording
Modify 4.3.3(14.1/5):
For the base_expression of a delta_aggregate[, if the nominal subtype of the delta_aggregate is a constrained array subtype], the applicable index constraint is [the constraint of the subtype] {that of the delta_aggregate as a whole, if any};
!discussion
Aggregates generally don't have nominal subtypes, so this bullet is reworded to avoid using that term.
!corrigendum 4.3.3(14.1/5)
Replace the paragraph:
• For the base_expression of a delta_aggregate, if the nominal subtype of the delta_aggregate is a constrained array subtype, the applicable index constraint is the constraint of the subtype;
by:
• For the base_expression of a delta_aggregate, the applicable index constraint is that of the delta_aggregate as a whole, if any;
!ACATS test
This rewording shouldn't change the needed ACATS test for this bullet.
!appendix
```
[Editor's note: From a private thread with many more topics in each message;
only the relevant part is given here.]

From: Jeff Cousins
Sent: Tuesday, November 9, 2021  3:16 AM

4.3.3(14.1/5) – the item being written to can have a nominal subtype, and
maybe the item used as the base expression, but can the delta aggregate
itself?

****************************************************************

From: Tucker Taft
Sent: Tuesday, November 9, 2021  9:18 AM

Not sure what you are asking here...

****************************************************************

From: Jeff Cousins
Sent: Tuesday, November 9, 2021  11:53 AM

4.3.3 (14.1/5) says “... if the nominal subtype of the delta_aggregate ...”

What is the nominal subtype  of a delta aggregate?  Taking the example from
4.3.4 (27/5), where in the following is a subtype named (other than Integer)?

((0 => 1.0, 1 => 2.0, 2 => 3.0)
with delta Integer(Random * 2.0) => 14.2)

****************************************************************

From: Tucker Taft
Sent: Tuesday, November 9, 2021  12:53 PM

This looks like a bug in the wording.  Aggregates generally don't have
"nominal" subtypes.  They are one of the few things that don't.
4.3.3(14.1/5) should probably say:

For the base_expression of a delta_aggregate[, if the nominal subtype of
the delta_aggregate is a constrained array subtype], the applicable index
constraint is [the constraint of the subtype] {that of the delta_aggregate
as a whole, if any};

****************************************************************
```

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