J3/04-301

Date:  4-May-2004
To:    J3
From:  JOR/interp/Stan Whitlock
Subj:  F95 interpretation #000023


NUMBER: 000023
TITLE: Termination of the previous record by a WRITE statement
KEYWORDS: Nonadvancing, Record termination, WRITE
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:

Suppose a sequential formatted file is positioned within a record as
a result of a nonadvancing READ.

1. If the next operation performed on the file is a WRITE, can the
   current record be terminated at its current position before the
   next record is written?  Section 9.2.1.3.2 appears to preclude the
   record from being terminated, but at least one Fortran 90
   implementation does the record in such an instance.

2. If next operation is a nonadvancing WRITE and the number of
   characters written does not extend to the end of the current
   record, are the remaining characters at the end of the record
   preserved?

ANSWER:

1. No.  If the current record were to be terminated, the file
   position would be changed.  Section 9.2.1.3.2 [136:37-39] states:
   "For sequential access on input, if there is a current record, the
   file position is not changed.  Otherwise, the file is positioned
   at the beginning of the next record and this record becomes the
   current record."

2. Yes.  The remaining characters in the record are preserved.

   Consider the following different, but related, example:

        program write_write
        write (10,"(a,t1,a,a)") "XXXXXXXXX", "ABC", "DEF"
        write (10,"(a,t1,a)",advance='no') "XXXXXXXXX", "ABC"
        write (10,"(a)") "DEF"
        end

   The output from this program is

        ABCDEFXXX
        ABCDEFXXX

   From the description of Position editing (10.6.1) it is clear
   that the output following the tab does not cause the deletion
   of the final XXX characters from the record.  The fact that the
   second output record is created by a non-advancing write
   followed by an advancing write is not operationally different
   from the single advancing write that created the first record.

   The fundamental difference between this example and the question
   considered in the interp is the mechanism by which the current
   location in the record is established prior to the final
   advancing write statement. It would be inconsistent to have one
   case preserve previously existing characters in the record and
   the other case to require the opposite.  To avoid this
   inconsistency, the answer to Question 2 is Yes.

EDIT:  None

SUBMITTED BY: Robert Corbett

HISTORY:  98-155    m145  Submitted (part 1)
          WG5/N1410       Draft answer
          01-151r1  m156  Passed unanimously by J3 meeting
          01-224r1  m157  Failed J3 letter ballot
          04-301    m168  Submitted for J3 meeting vote