J3/13-250
To: J3
From: Van Snyder
Subject: Interp F08/0071
Date: 2013 February 14

1. Introduction

Interp F08/0071 failed with a NO vote from John Reid, and a comment
from Van Snyder.  The reasons for the NO vote and comment have been
addressed by Corrigendum 1.

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NUMBER: F08/0071
TITLE: Vector subscript target
KEYWORDS: Pointer assignment, Vector subscript
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:

Consider

  PROGRAM m197006
    REAL,TARGET :: x(100) = [ (i,i=1,100) ]
    REAL,POINTER :: p(:)
    TYPE t
      REAL,POINTER :: q(:)
    END TYPE
    TYPE(t) y
    p => x                     ! (1)
    y = t(x)                   ! (2)
    p => x( [ 1,4,9,25 ] )     ! (3)
    y = t(x( [ 1,4,9,25 ] ))   ! (4)
    PRINT *,y%q
  END PROGRAM

The pointer assignment statement at (1) associates P with X.
The intrinsic assignment statement at (2) includes the effect of
pointer assignment of X to Y%Q, but is not a pointer assignment
statement.

The pointer assignment statement at (3) is not standard-conforming
according to 6.5.3.3.2 paragraph 2:
  "An array section with a vector subscript shall not be
   ... the <data-target> in a pointer assignment statement"

However, the intrinsic assignment statement at (4) is not subject to
this requirement as it is not a pointer assignment statement.

Note that the quoted paragraph is entirely  duplicative, as in:
 - the first bullet item is covered by 12.5.2.4p18,
 - the second bullet item is covered by C724 in 7.2.2.2
   (but C724 does not cover this case either),
 - the third bullet item is covered by C901 in 9.5.1.
Editorial improvements have been made in corrigendum 1.  The entire
paragraph has been rewritten.

Q1. Was the statement marked (4) intended to be allowed?

Q2. If not, was it intended to be prohibited by a constraint like
    C724, or was it intended to be a simple requirement?
    (Editorial note: in any case surely the requirement should appear
    in the pointer assignment subclause.)

ANSWER:

A1. No, this was not intended.  An edit is supplied to correct this.

A2. Constraint C724 was intended to cover this case.  An edit is
    supplied to correct this.

EDIT:

[158:19-20] In 7.2.2.2 Syntax of the pointer assignment statement,
            C724, change ""(R737) A <variable>"
            to "A variable that is a pointer target",
            making the whole constraint read:
  "A variable that is a pointer target shall have either the TARGET
   or POINTER attribute, and shall not be an array section with a
   vector subscript."
{Make the constraint apply to all forms of pointer assignment.}

{Notice that this edit incorporates the list item concerning vector
subscripts from 6.5.3.3.2p2 status quo ante corrigendum 1.}

SUBMITTED BY: Malcolm Cohen

HISTORY: 12-121    m197  F08/0071 submitted
	 12-121r1  m197  Revised wording with same edits - passed
                          by J3 meeting
         12-165r2  m198  Failed J3 letter ballot #25 12-147
         13-nnn    m200  Revised

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