J3/10-180r1
To: J3
From: Malcolm Cohen/Stan Whitlock
Subject: Interp on unlimited format repeat
Date: 2010 June 14

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NUMBER: F08/0030
TITLE: Unlimited format repeat effects
KEYWORDS: repeat count
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:

Consider the program

Program example
  Integer :: x(3) = (/ 1,2,3 /)
  Print 1,x
1 Format(1x,999999999('a',I0,'b'))
  Print 2,x
2 Format(1x,*('a',I0,'b'))
  Print 3,x
3 Format(1x,999999999('a',:,',',I0,'b'))
  Print 4,x
4 Format(1x,*('a',:,',',I0,'b'))
End Program

According to the first statement of 10.4p8 [249:12-13],

  "If format control encounters the rightmost parenthesis of a
   complete format specification and another effective item is not
   specified, format control terminates."

This means that the first two lines of output should be
 a1ba2ba3ba
 a1ba2ba3b

and the second two lines of output should be
 a,1ba,2ba,3ba
 a,1ba,2ba,3b

But according to Note 10.7,

  "The effect of an unlimited-format-item is as if its enclosed list
   were preceded by a very large repeat count."

which it manifestly is not.

Is the normative text correct or the note?

ANSWER:

The note is correct.  In the exmaple above the output of the first two
lines should be the same and equal to the first of the two lines and
the second two lines should be the same and equal to the first of those
two lines.

An edit is supplied to correct the normative text.

To make the following example non-standard:

    print 20
 20 format { *('a') )

the reused portion of the unlimited format item must contain at least
one data edit descriptor.

A constraint is provided.

EDITS to 10-007:

[246:15] After C1002 in 10.3.1, add a new constraint:

  "C10xx (R1005) An <unlimited-format-item> shall contain at least
                 one data edit descriptor."

[249:11+] Insert after the seventh paragraph of 10.3.3 a new paragraph:

  "If format control encounters the rightmost parenthesis of an
   unlimited format item, format control revert to the leftmost
   parenthesis of the unlimited format item."

SUBMITTED BY: Malcolm Cohen

HISTORY: 10-180    m192  F08/0030 submitted
         10-180r1  m192  Draft answer

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