J3/01-302

Date:    6 August 2001
To:      J3
From:    WG5 Members
Subject: Interp 91 (Definition of "present" is defective)

WG5 members in London considered Interp 91 and recommend as
follows. The HISTORY mentions the action recommended by WG5.

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NUMBER: 000091
TITLE: Definition of "present" is defective
KEYWORDS: present, dummy argument
DEFECT TYPE: Erratum
STATUS: J3 consideration in process

QUESTION:

Subclause 12.4.1.5 begins with a definition of the term "present":

"A dummy argument is present in an instance of a subprogram if it is
associated with an actual argument and the actual argument either is a
dummy argument that is present in the invoking subprogram or is not a
dummy argument of the invoking subprogram."

This seems to be defective in that if the actual argument is a dummy
argument that is accessed by host association, it is not a dummy
argument OF the invoking subprogram, and therefore although it may be
"not present" in the procedure of which it is a dummy argument, it is
nonetheless "present" in an internal procedure of that procedure.

Consider:

  module M
  contains
    subroutine S1 ( A )
      integer, optional :: A
      call S11
    contains
      subroutine S11
        call S12 ( A )
      end subroutine S11
      subroutine S12 ( B )
        integer, optional :: B
        if ( present(B) ) print *, 'B is present'
      end subroutine S12
    end subroutine S1
  end module M

  program P
    use M, only: S1
    call S1
  end program P

Should this print "B is present" as implied by the above analysis?

ANSWER:

No, the program should not print anything.

DISCUSSION:

The lack of consideration of host association in the cited text is
accidental; an edit is supplied to correct this oversight.

EDITS:

[202:43-45] Replace the first sentence of 12.4.1.5 by
"A dummy argument or an entity that is host associated with a dummy
argument is not <<present>> if the dummy argument
(1) is not associated with an actual argument, or
(2) is associated with an actual argument that is not present.
Otherwise, it is present."

[299:4-6] Delete the glossary entry for <<present>>

SUBMITTED BY: Van Snyder

HISTORY: 01-134   m156 Submitted
         01-134r1 m156 Passed unanimously by J3 meeting
         01-224r1 m157 Passed by J3 letter ballot
         WG5-N1395     Failed WG5 letter ballot
         WG5-N1463     Accept Kurt Hirchert's suggestion with minor edits