To: J3                                                     J3/10-140
From: Stan Whitlock
Subject: F2008 edits for interp F03/0090
Date: 2010 February 16

1. Introduction

Interp F03/0090 passed as amended in WG5 ballot #7 {N1805/6/16}.
These comments were accepted:

  * Long comment

    Should the edit for [68:9] also be applied to [68:11]? YES

  * Cohen no

    There is no edit that prohibits an array contructor ac-value from
    being unlimited polymorphic (i.e. CLASS(*)); we should state this
    directly, not make people infer it from more difficult rules.
    Proposed fix:
     [67:19+] Insert new constraint
       "An <ac-value> shall not be unlimited polymorphic.".

2. The final form of F03/0090 is

NUMBER: F03/0090
TITLE:  Polymorphic array constructors
KEYWORDS: polymorphic, array constructor
DEFECT TYPE: Erratum
STATUS: Passed by WG5 ballot

QUESTION:

(1) Consider

  FUNCTION f1(dummy,n)
    CLASS(t) dummy
    TYPE(t) f1(n)
    f1 = [ (dummy,i=1,n) ]
  END FUNCTION

Is this standard-conforming?

(2) If the array constructor elements are polymorphic, is the array
    constructor polymorphic with the dynamic type of the elements?
    For example, consider

  FUNCTION f2(dummy,n)
    CLASS(t) dummy
    CLASS(t),ALLOCATABLE :: f2(:)
    IF (...) THEN
      ALLOCATE(f2(n),SOURCE=[(dummy,i=1,n)])   ! **1
    ELSE
      ALLOCATE(f2(n),SOURCE=dummy)             ! **2
    END IF
  END FUNCTION

The second ALLOCATE statement (marked **2) clearly allocates F2 with
size N and the dynamic type of DUMMY.

If the array constructor is polymorphic, the first ALLOCATE statement
(marked **1) will have the same effect, otherwise it will allocate F2
with the dynamic type of F2 equal to the declared type of DUMMY.

(3) If the array constructor is polymorphic, what is the dynamic type
    when multiple items have different dynamic types?

ANSWER:

(1) Yes.

(2) No, it was not intended for array constructors to be polymorphic.
    A polymorphic array value, if desired, can be safely constructed
    by using an allocatable array function.

(3) Not applicable.

An edit is provided to clarify the situation.

EDITS:

[67:19+] Insert new constraint
       "CXXX (R469) An <ac-value> shall not be unlimited polymorphic.".

[67:21] "same type" -> "same declared type"

[68:9] "type and" -> "declared type and"

[69:11] "type and" -> "declared type and"

[68:14+] Insert new paragraph
  "The dynamic type of the array constructor is the same as its declared
   type."

SUBMITTED BY: Van Snyder

HISTORY: 07-231    m180  F03/0090 submitted (revised by M. Cohen)
         07-231    m180  Passed by J3 meeting
         07-272    m181  Failed J3 letter ballot #13 07-250r1
         09-266    m189  Revised answer - Passed by J3 meeting
         09-295    m190  Passed as amended by J3 letter
                          ballot #19 09-292
         N1816     m191  Passed as amended by WG5 ballot #7 {N1805/6}

3. Edits to fix F2008 09-007r3 to include the edits from F03/0090

EDITS:

[85:3+] Insert new constraint
       "CXXX (R472) An <ac-value> shall not be unlimited polymorphic.".

[85:4] "same type" -> "same declared type"

[85:14] "type and" -> "declared type and"

[85:15] "type and" -> "declared type and"

[85:18+] Insert new paragraph
  "The dynamic type of the array constructor is the same as its declared
   type."