[J3] surprisingly PURE
Steven G. Kargl
kargl at troutmask.apl.washington.edu
Sun Apr 19 18:47:27 EDT 2020
On Sun, Apr 19, 2020 at 08:43:24PM +0000, Bill Long via J3 wrote:
>> On Apr 19, 2020, at 2:16 PM, Steve Lionel via J3 <j3 at mailman.j3-fortran.org> wrote:
>> I admit that I am not all that good as a language lawyer, but I
>> think Steve K has it right.
>> C1594 says (with irrelevant parts removed):
>> In a pure subprogram any designator with a base object that
>> is in common or accessed by host or use association
> The base object is Y which is local to the subprogram.
>> ,... or an object that is storage associated with any such
>> variable, shall not be used
>> (1) in a variable definition context (19.6.7),
> Defining a pointer IS defining the target of the pointer. X is
> host associated. Defining y%p is defining X and so it might be
> already covered.
> Certainly disallowing this case is consistent with the intention
> that PURE procedures do not modify non-argument-asscoiated
> variables outside their scope.
I think we're looking for
126.96.36.199 Pointer definition status
The definition status of an associated pointer is that of its
target. If a pointer is associated with a definable target, it
becomes defined or undefined according to the rules for a variable
Y%P is associated with the host-associated variable X. Doesn't
C1594 (1) then apply as X cannot appear in variable definition
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