J3/00-124

Date:     24th February 2000
To:       J3
From:     Malcolm Cohen
Subject:  Interpretation Request: Scope of ac-implied-DO variable

NUMBER:
TITLE:  Scope of array-constructor implied-DO variable
KEYWORDS:
DEFECT TYPE:
STATUS: J3 consideration in progress
QUESTION:

14.1.3 states that the scope of an implied-DO variable in an array
constructor
is "the implied-DO list".  There is no such syntax term: what is meant?

In particular, in the array constructor

  (/ (I,I=1,I) /)

are all three I's references to the implied-DO variable, or is one of them
a reference to a variable I in the enclosing scoping unit?

ANSWER:

All occurences of I within the implied-DO are references to the implied-DO
variable, none of them can reference a variable in the enclosing scoping
unit.

The term "implied-DO list" is confusing in this context; "implied-DO" was
intended.  An edit is supplied for clarification.

DISCUSSION:

The term "implied-DO list" is used in several places where the context is
that of the values produced by the implied-DO.  This is an inappropriate
term to use for specifying scope.

Also, the second and third occurrences of "I" in the example shown are part
of
the syntax item <ac-implied-do-control>.  It would be unreasonable to read
"implied-DO list" as meaning (for array constructors) "<ac-value-list> and
the
<ac-do-variable> in <ac-implied-do-control> but not the <scalar-int-expr>s
in
<ac-implied-do-control>."

Note that the problem does not arise for <data-implied-do> because variables
other than implied-DO variables are not permitted in the limit expressions.

With this interpretation the example array constructor supplied is not valid
Fortran, as it is not permissible to reference the value of an
<ac-implied-do>
variable in one of its limit expressions.

EDITS:

[280:41] Replace "implied-DO list" with "implied-DO".

SUBMITTED BY: Malcolm Cohen
HISTORY: 152-mjc-9  m152  submitted

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