[J3] surprisingly PURE

Vipul Parekh parekhvs at gmail.com
Tue Apr 21 09:19:07 EDT 2020

On Tue, Apr 21, 2020 at 12:11 AM Malcolm Cohen via J3 <
j3 at mailman.j3-fortran.org> wrote:

> Hi Vipul,
> Thanks for the comments.
> Unfortunately your simple constraint doesn’t work, as an intervening
> pointer assignment, structure constructor, **or call to another pure
> procedure** makes it ineffective. As worded, it does not even forbid
> Robert’s example, though that is fixable. ..

Hello Malcolm,

Thanks for your feedback.

I did view the phrasing of the simple constraint I suggested as merely an
exercise to learn how to compose an edit to the standard as you suggested
in one of your earlier notes!

And I did have both Bob's example as well as Van's (with local object
"instantiation" using MOLD and definition in a polymorphic context) in
mind.  I thought the wording I suggested prohibits "Y%P = 2.0" instruction
in Bob's example as well as "Y%P = 42.0" in Van's, thus rendering them both
non-conforming relative to a further standard revision that fixes this
"defect" (as you called it).

So I'm curious and would like to learn more about "As worded, it does not
even forbid Robert’s example, though that is fixable. ..".   Can you please
elaborate a little on how the wording I suggested fails to forbid Bob's
example even?

Your explanation will also be valuable highly I think to other committee
members, particularly those who have joined recently, on how to author the
standard with proper wording that captures the desired objectives of any
given change.

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